Volodymyr Zelenskyy warns NATO as Russia strikes near Polish border

Ukrainian President Volodymyr Zelenskyy warned NATO Monday that its member states would soon be attacked by Russian forces after an air strike hit a Ukrainian military base close to the Polish border.

Meanwhile, the death toll in the strategic southern port city of Mariupol, facing acute deprivation amid a prolonged siege, has topped 2,000, officials there said.

While western Ukraine has largely been spared so far, Russian air strikes overnight Saturday into Sunday carried the war deep into the west, killing 35 people and wounding 134 at a military base near Yavoriv, outside the city of Lviv -- which is dangerously close to the frontier with EU and NATO member Poland.

"If you do not close our sky, it is only a matter of time before Russian missiles fall on your territory, on NATO territory, on the homes of NATO citizens," Zelenskyy said in a video address released shortly after midnight, urging NATO to impose a no-fly zone over his country.

Washington and its EU allies have sent funds and military aid to Ukraine and imposed unprecedented economic sanctions on Russia.

Zelenskyy has continued to implore foreign counterparts to do more.

Read | UN says 596 civilians killed since Ukraine war began

"Last year, I clearly warned NATO leaders that if there were no harsh preventive sanctions against the Russian Federation, it would go to war," Zelenskyy said. "We were right."

Further east, the latest fighting in Kyiv's suburbs left a US journalist dead -- the first foreign reporter killed since Russia's invasion of its neighbour on February 24.

"Kyiv. A city under siege," presidential advisor Mykhailo Podolyak wrote on Twitter. He said the city was preparing a "ruthless defence".

Meanwhile, efforts continued to get help to Mariupol, which aid agencies say is facing a humanitarian catastrophe.

A humanitarian column headed there had to turn back again on Sunday, a city official told AFP, after the Russians "did not stop firing."

A total of 2,187 residents have now died in days of relentless Russian bombardment, the city council said Sunday.

"The enemy is holding the city hostage by performing real acts of genocide," said Ukraine Defense Minister Oleksiy Reznikov.

Zelenskyy has accused Moscow of both blocking and attacking humanitarian convoys, although he said Sunday that another 125,000 people had been evacuated that way across Ukraine.

"Russians are bombing the city even during official negotiations," Defence Minister Reznikov said. "They have no dignity, no honor, no mercy."

Talks between the two sides have yet to yield a ceasefire, but Ukrainian and Russian representatives will meet via video-conference Monday, a Zelenskyy adviser and a Kremlin spokesman both said.

"And our goal is that in this struggle, in this difficult negotiating work, Ukraine will get the necessary result... for peace and for security," Zelenskyy said early Monday.

"We see significant progress," Leonid Slutsky, a senior member of Russia's negotiating team, told state-run television network RT Sunday.

Russia's forces had earlier focused on eastern and southern areas of Ukraine -- home to more ethnic Russians -- but in recent days have moved to the country's centre, striking the city of Dnipro, and now to the west with the attack at military base in Yavoriv near Poland, which had been a training centre for Ukrainian forces with foreign instructors.

Pentagon spokesman John Kirby told ABC that Russia was "clearly, at least from an air strike perspective... broadening their target sets".

An AFP reporter said the wounded from the military training centre -- some limping, some pushed in wheelchairs or carried on stretchers -- were loaded into tens of ambulances that shuttled between Yavoriv and Lviv carrying victims to hospitals. Military trucks brought injured soldiers to the hospital in nearby Novoyavorivsk.

Locals rushed to hospitals to offer help. "I came here to donate blood, but I was put on the waiting list," Mariya Antonyshyn, a school psychologist, told AFP outside the Novoyavorivsk hospital.

Meanwhile in Kyiv, only the roads to the south remain open, according to the Ukrainian presidency. City authorities have set up checkpoints, and people are stockpiling food and medicine.

The northwestern suburb of Bucha is entirely held by Russian forces, along with parts of Irpin, Ukrainian soldiers told AFP. Some blocks in the once well-to-do suburb have been reduced to rubble.

An American journalist, award-winning video documentary maker Brent Renaud, was shot dead, and an American photojournalist with him, Juan Arredondo, was wounded Sunday in Irpin, medics and witnesses said.

Britain's defence ministry said Saturday that Russian forces were about 25 kilometres (15 miles) from Kyiv and that a column north of the city had dispersed as part of an apparent attempt to encircle it.

However, the Russians are encountering resistance from the Ukrainian army to both the east and west of the capital, according to AFP journalists on the scene.

"They have to camp in villages in temperatures of nearly minus 10 Celsius at night. They lack provisions and have to raid houses," said one soldier, Ilya Berezenko, 27.

The UN estimates that almost 2.7 million people have fled Ukraine since the invasion, most of them to Poland, which is struggling to provide for the arrivals.

Pope Francis on Sunday issued an impassioned plea to the Russians, saying, "In the name of God, I ask you, stop this massacre!".

Zelenskyy says the Russians have suffered "heavy losses" of about 12,000 troops -- although Moscow put the number at 498, in its only toll released March 2.

About 1,300 Ukrainian troops have been killed, according to Kyiv.

Four people were killed and three injured in a strike on the Black Sea city of Mykolaiv, a strategic hub on the road to Odessa that has been under attack for days, authorities said Sunday.

"Those bastards just dropped a bomb from a plane on the school," said Mykolaiv Mayor Vitaly Kim.

Meanwhile, in the eastern Donbas region, a senior Ukrainian police officer accused Russia of using phosphorus chemical bombs around Popasna.

Further south, bombs struck the Sviatoguirsk monastery, where nearly 1,000 civilians were sheltering, wounding 30 people, a Ukrainian official said.

In the southern Ukrainian city of Kherson, Russian troops fired warning shots after thousands of locals gathered to protest the invasion, local media said.

And in Russia itself, more than 800 people were detained during anti-war demonstrations.

The Ukraine president -- who has maintained an extraordinarily high profile through the conflict -- visited wounded soldiers at a hospital outside Kyiv, which was shown in a video released Sunday.

"Feel better, stay strong," a visibly moved Zelenskyy told them. "You are doing a great job."

He referred to his visit during his address early Monday, praising Ukrainian doctors for treating wounded Russians at the same facility.

"Because they are people, not beasts," he said. "And we have to go through this war so that we all remain human."

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