Russia has escalated attacks in western Ukraine, striking a military base where its troops had trained with NATO forces and bringing the conflict closer to Poland and other members of the bloc.

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The Ukrainians said that over 30 cruise missiles were fired at the base located 30 kilometres (19 miles) northwest of regional hub Lviv, killing at least nine people and wounding 57. No further information on the casualties was immediately available.

A day earlier, a senior Russian diplomat said Moscow had warned the United States that it considered foreign shipments of military equipment to Ukraine “legitimate targets,” and thus fair game for attack.

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It was unclear immediately what the base was being used for US President Joe Biden has announced an additional aid to Ukraine of up to $200 million for weapons, military services, education and training — atop $6.5 billion of military aid already approved.

Now in its third week, the war has forced more than 2.5 million people to flee Ukraine.

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Here are some key things to know about the conflict:

What is happening in besieged Mariupol?

Russian shelling of this Ukrainian port city of 430,000 has been relentless, and the mayor’s office says more than 1,500 have died since the siege began. Russian forces hammered the city’s downtown on Saturday as residents hid.

Repeated attempts to bring food to Mariupol and evacuate civilians have been cancelled due to ongoing Russian fire. The unceasing shelling has even interrupted efforts to bury the dead in mass graves.

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On Saturday, a Ukrainian official said Russian soldiers blocked a humanitarian convoy headed for Mariupol and stole from another. Doctors Without Borders said some residents are dying for lack of medication, with the city without drinking water or medicine for over a week now. The aid group says people are resorting to boiling water from the ground or extracting it from heating pipes.

What has the media witnessed?

An Associated Press journalist witnessed tanks firing on a 9-story apartment block in Mariupol and was with a group of medical workers who came under sniper fire on Friday. Conditions at a local hospital there were deteriorating, electricity was reserved for operating tables and the hallways were lined with people with nowhere else to go.

Anastasiya Erashova wept and trembled as she held a sleeping child. The shelling had just killed her other child as well as her brother’s child. “No one was able to save them,” she said.

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In Irpin, on the northwest outskirts of Kyiv, bodies laid in the open in a park and on a street Saturday. Residents said they had no information about what or where was safe as the shooting echoed.

What else is happening elsewhere on the ground in Ukraine?

In the northeast, Russian forces were blockading Kharkiv, Ukraine’s second-largest city, even as efforts have been made to create new humanitarian corridors around it and other urban centres.

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In multiple areas around Kyiv, heavy artillery fire sent residents scurrying for shelter as air raid sirens wailed. An ammunition depot outside the city was shelled overnight, sending billowing black smoke into the sky, according to a video provided by emergency workers.

The most vulnerable

Ukraine’s chief prosecutor’s office says at least 85 children have been killed since the invasion began on Feb. 24, and over 100 wounded. At least 2.5 million people have fled the country, according to the United Nations refugee agency.

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About 60 child cancer patients from Ukraine boarded a medical train Saturday in Medyka, Poland, bound for hospitals in Warsaw and elsewhere. Medical workers carried some of the children in their arms, on stretchers and pushed them in wheelchairs at the train station near the Ukrainian border.

Dominik Daszuta, an anesthesiologist from Warsaw Hospital, said the train has transported 120 children with cancer so far.