MARIUPOL, Ukraine (AP) — An airstrike on a hospital in the port of Mariupol killed three people, including a child, the city council said Thursday, and Russian forces intensified their siege of Ukrainian cities, even as the top diplomats from both sides met for the first time since the war began.

The attack a day earlier in the besieged southern city wounded 17 people, including women waiting to give birth, doctors and children buried in the rubble. Bombs also fell on two hospitals in another city west of the capital, Kyiv.

The World Health Organization said it has confirmed 18 attacks on medical facilities since the Russian invasion began two weeks ago.

As the war entered its third week, Western officials said Russian forces have made little progress on the ground in recent days, but they have intensified the bombardment of Mariupol and other cities, trapping hundreds of thousands of people, with food and water running short. Temporary cease-fires to allow evacuations have often faltered, with Ukraine accusing Russia of continuing their bombardments. But Ukrainian President Volodymyr Zelenskyy said 35,000 people managed to get out on Wednesday from several besieged towns.

The Mariupol city council posted a video Thursday showing buses driving down a highway, with a note saying that a convoy bringing food and medicine was on the way despite several days of thwarted efforts to reach the city.

Images from the city, where hundreds have died and some victims have been buried in a mass grave, have drawn condemnation from around the world. Britain called the attack on a children's hospital a war crime. Two other hospitals were also hit in Zhytomyr, a city west of Kyiv, Mayor Serhii Sukhomlyn said on Facebook. He said there were no injuries.

“Everyone is working to get help to the people of Mariupol. And it will come,” said Mariupol Mayor Vadym Boychenko.

On the western edge of Kyiv, artillery fire could be heard Thursday, Deputy Interior Minister Vadym Denysenko said. He told Ukrainian TV channel Rada that residents had a “rather difficult” night on the outskirts of the capital in which Russian forces started by targeting military sites but then hit residential areas.

Meanwhile, the sides held their highest-level talks so far Thursday. President Recep Tayyip Erdogan said he hoped the meeting between Russian Foreign Minister Sergey Lavrov and his Ukrainian counterpart Dmytro Kuleba in a Turkish Mediterranean resort “will open the door to a permanent cease-fire.”

Kuleba said the two sides discussed a 24-hour cease-fire but did not make progress. He said Russia was still seeking “a surrender from Ukraine.”

“This is not what they are going to get,” he said, adding that he was willing to continue the dialogue.

The ground shook more than a mile away when the series of blasts hit a children's and maternity hospital in Mariupol. Explosions blew out windows and ripped away much of the front of one building. Police and soldiers rushed to the scene to evacuate victims, carrying a bleeding woman with a swollen belly on a stretcher past burning and mangled cars.

Another woman wailed as she clutched her child. In the courtyard, a blast crater extended at least two stories deep.

“Today Russia committed a huge crime,” said Volodymir Nikulin, a top regional police official, standing in the ruins. “It is a war crime without any justification.”

President Zelenskyy said the Mariupol strike trapped children and others under debris.

“A children’s hospital. A maternity hospital,” Zelenskyy said in his nightly video address, switching to Russian to express horror at the strike. “What kind of country is this, the Russian Federation, which is afraid of hospitals, afraid of maternity hospitals, and destroys them?”

Sharing video that showed cheerfully painted hallways strewn with twisted metal, Zelenskyy urged the West to impose even tougher sanctions than the ones that have already plunged its economy into severe isolation, so Russia “no longer has any possibility to continue this genocide.”

Britain’s Armed Forces minister, James Heappey, said that whether hitting the hospital was “indiscriminate” fire into a built-up area or a deliberate targeting, “it is a war crime.”

On Thursday, Britain added more oligarchs to its sanctions list, including Roman Abramovich, the billionaire Premier League soccer club Chelsea. The government said Abramovich’s assets were frozen, he was banned from visiting the U.K. and barred from transactions with U.K. individuals and businesses.

Russia’s military is struggling more than expected, but Putin’s invading force of more than 150,000 troops retains possibly insurmountable advantages in firepower as it bears down on key cities.

Despite often heavy shelling on populated areas, American military officials reported little change on the ground over the previous 24 hours, other than Russian progress against the cities of Kharkiv and Mykolaiv, in heavy fighting. The officials spoke on condition of anonymity to assess the military situation.

Authorities announced new cease-fires to allow thousands of civilians to escape bombarded towns. Zelenskyy said three humanitarian corridors operated on Wednesday, from Sumy in the northeast near the Russian border, from suburbs of Kyiv and from Enerhodar, the southern town where Russian forces took over a large nuclear plant.

In all, he said, about 35,000 people got out. More evacuations were planned for Thursday from towns and cities under bombardment in eastern and southern Ukraine — including Mariupol — as well as the Kyiv suburbs.

People streamed out of Kyiv’s suburbs a day earlier, many headed for the city center, as explosions were heard in the capital and air raid sirens sounded repeatedly. From there, the evacuees planned to board trains bound for western Ukrainian regions not under attack.

Civilians leaving the Kyiv suburb of Irpin were forced to make their way across the slippery wooden planks of a makeshift bridge, because the Ukrainians blew up the concrete span leading to Kyiv days ago to slow the Russian advance.

With sporadic gunfire echoing behind them, firefighters dragged an elderly man to safety in a wheelbarrow, a child gripped the hand of a helping soldier, and a woman inched her way along, cradling a fluffy cat inside her winter coat. They trudged past a crashed van with the words “Our Ukraine” written in the dust coating its windows.

Previous attempts to establish safe evacuation corridors over the past few days largely failed because of what the Ukrainians said were Russian attacks. But Putin, in a telephone call with Germany’s chancellor, accused militant Ukrainian nationalists of hampering the evacuations.

International Red Cross spokesman Jason Straziuso said safe passage corridors were welcome but have to be well planned, with details agreed on by all sides including the right to bring in food, clean water, medical supplies and other necessities.

Such guarantees are vital for places like Mariupol, a city of 430,000 on the Sea of Azov, where Zelenskyy's office said about 1,200 people have died during the nine-day siege.

Local authorities hurried to bury the dead from the past two weeks of fighting in a mass grave in the city. Workers dug a trench some 25 meters (yards) long at one of the city’s old cemeteries and made the sign of the cross as they pushed in bodies wrapped in carpets or bags.

Nationwide, thousands are thought to have been killed, both civilians and soldiers, since Putin’s forces invaded. The U.N. estimates more than 2 million people have fled the country, the biggest exodus of refugees in Europe since the end of World War II.

The fighting knocked out power to the decommissioned Chernobyl nuclear plant on Wednesday, raising fears about the spent radioactive fuel stored there that must be kept cool. But the U.N. nuclear watchdog agency said it saw “no critical impact on safety” from the loss of power.

Ukrainian Deputy Prime Minister Iryna Vereshchuk pleaded Thursday with the Russian military to allow access for repair crews to restore electricity to the plant, and to fix a damaged gas pipeline in the south that has left Mariupol and other towns without heat for days.

The crisis is deteriorating as Moscow’s forces intensify their bombardment of cities in response to what appears to be stronger Ukrainian resistance and heavier Russian losses than anticipated.

The Biden administration warned Russia might seek to use chemical or biological weapons in Ukraine and rejected Russian claims of illegal chemical weapons development there.

This week, Russian Foreign Ministry spokeswoman Maria Zakharova — without evidence — accused Ukraine of running chemical and biological weapons labs with U.S. support. White House press secretary Jen Psaki called the claim “preposterous” and said Russia might be trying to lay the groundwork for its own use of such weapons against Ukraine.

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Associated Press journalists Yuras Karmanau in Lviv, Ukraine, and Felipe Dana and Andrew Drake in Kyiv, Ukraine, contributed along with other reporters around the world.