LVIV, Ukraine--Russian forces launched a missile attack on a large Ukrainian military facility near the Polish border on Sunday, Ukrainian officials said, in what appeared to be the westernmost attack of the war.

"The occupiers launched an air strike on the International Center for Peacekeeping and Security" in Yavoriv, the Lviv regional military administration said in a statement. "According to preliminary data, they fired eight missiles."

Reuters was unable immediately to verify the report and Russia offered no immediate comment.

Initial reports indicated "there are no dead, but information about the injured and wounded is being clarified," said Anton Mironovich, spokesman for the Academy of Land Forces of the Ukrainian Armed Forces, according to Interfax Ukraine news agency.

Nineteen ambulances with sirens on were seen by Reuters driving from the direction of the Yaroviv facility after the strike.

The 360 square-km (140 square-mile) facility less than 25 km (15 miles) from the Polish border, is one Ukraine's biggest and the largest in the western part of the country.

Ukraine held most of its drills with NATO countries there before the invasion. The last major exercises were in September.

The mayor of another city in western Ukraine, Ivano-Frankivsk, said Russian troops also continued to hit its airport, with no initial reports of casualties.

In eastern Ukraine, Russian troops are trying to surround Ukrainian forces as they advance from Kharkiv in the north and Mariupol in the south, the UK Defence Ministry said on Sunday.

"Russian forces advancing from Crimea are attempting to circumvent Mykolaiv as they look to drive west towards Odessa," the ministry said in an intelligence update posted on Twitter.

Air raid sirens again woke residents in Kyiv on Sunday morning, hours after Ukrainian President Volodymyr Zelenskiy warned Russian forces they face a fight to the death if they try to occupy the capital.

"If they decide to carpet bomb and simply erase the history of this region ... and destroy all of us, then they will enter Kyiv. If that's their goal, let them come in, but they will have to live on this land by themselves," Zelenskiy said on Saturday.

Russian shelling has trapped thousands of people in besieged cities and sent 2.5 million Ukrainians fleeing to neighbouring countries.

Ukraine accused Russian forces on Saturday of killing seven civilians in an attack on women and children trying to flee fighting near Kyiv. France said Russian President Vladimir Putin had shown no readiness to make peace.

The Ukrainian intelligence service said the seven, including one child, were killed as they fled the village of Peremoha and that "the occupiers forced the remnants of the column to turn back."

Reuters was unable immediately to verify the report and Russia offered no immediate comment.

Moscow denies targeting civilians since invading Ukraine on Feb. 24. It blames Ukraine for failed attempts to evacuate civilians from encircled cities, an accusation Ukraine and its Western allies strongly reject.

‘NEED TO HOLD ON’

"We still need to hold on. We still have to fight," Zelenskiy said in a video address late on Saturday, his second of the day.

The United States said it would rush up to $200 million in additional small arms, anti-tank and anti-aircraft weapons to Ukraine, where officials have pleaded for more military aid.

The Kremlin describes its actions as a "special operation" to demilitarise and "deNazify" Ukraine. Ukraine and Western allies call this a baseless pretext for a war of choice that has raised fears of wider conflict in Europe.

Russian Deputy Foreign Minister Sergei Ryabkov accused the United States of escalating tensions and said the situation had been complicated by convoys of Western arms shipments to Ukraine that Russian forces considered "legitimate targets".

In comments reported by the Tass news agency, Ryabkov made no specific threat. Any attack on such convoys before they reached Ukraine would risk widening the war.

Crisis talks between Moscow and Kyiv have been continuing by video link, said Kremlin spokesperson Dmitry Peskov, according to Russia's RIA news agency. He gave no details, but Ukrainian Foreign Minister Dmytro Kuleba said Kyiv would not surrender or accept any ultimatums.

Russian troops have destroyed 3,687 Ukrainian military infrastructure facilities so far, Russian Defence Ministry spokesman Igor Konashenkov was quoted by Russian news agencies as saying on Sunday. It was not possible to independently verify his statement.

The Donetsk region's governor said constant shelling was complicating bringing aid into Mariupol. Fires were burning in the western section of the city and dozens of apartment buildings heavily damaged, according to images taken on Saturday by private U.S. satellite firm Maxar.