Kyiv fears Russia is seeking to press its advantage on the battlefield ahead of symbolic May 9 Victory Day celebrations, as both sides continued to launch deadly cross-border strikes.

A Ukrainian security source told AFP that Russia wanted to damage Ukrainian railway infrastructure to "paralyse deliveries and movement of military cargo" as Moscow prepares to advance.

"These are standard steps ahead of an offensive," the source added.

Russian forces have a firepower and manpower advantage at the front lines, and Kyiv has warned that fighting will become increasingly difficult in the coming weeks.

US Defense Secretary Lloyd Austin on Friday announced a $6 billion military aid tranche, which is its largest ever for Ukraine and will include interceptors for both Patriot and NASAMS air defense systems.

The package is the second this week, after President Joe Biden signed a much-delayed bill to provide a total $61 billion of new funding for Ukraine.

- Costly delays -

Ukrainian President Volodymyr Zelensky said he believed the Kremlin wants its army to capture the strategic heights of Chasiv Yar, a village in the eastern Donetsk region, before May 9, when Russia celebrates the Soviet Union's victory in World War II.

On Friday, he said the months of delays to US aid had cost his forces.

"While we were waiting for a decision on the American support, the Russian army managed to seize the initiative on the battlefield," he told a video meeting of dozens of Ukraine's international supporters.

Oleksandr Pertsovsky, head of passenger transport at state rail group Ukrzaliznytsia, confirmed that Russia had escalated its attacks on railway sites.

"They're hitting the stations indiscriminately. It's a very primitive way of doing it," he said.

Three railway employees were killed and four wounded in a Russian missile attack on the eastern Donetsk region Thursday, the company said.

Ten civilians were also injured Thursday when Russian forces attacked railway facilities in Balakliya in the Kharkiv region.

The Russian defence ministry said Friday that a strike on Udachne in the Donetsk region had targeted what it said were "Western weapons and military equipment" being transported by railway.

It also said it had struck railway loading facilities at Balakliya.

Those strikes represent just a small number of the attacks that have damaged trains or stations across Ukraine, including in more central regions like Cherkasy and Dnipro.

One of the deadliest single strikes of the war was on a railway station in Kramatorsk in April 2022, which killed more than 60 people fleeing Russia's advancing troops.

- Hospitals evacuated -

On Friday afternoon, Kyiv officials said they were urgently evacuating two hospitals in the capital after reports of a possible imminent Russian attack.

"A video is being widely circulated in the online media, actually announcing an enemy attack on these medical facilities," the Kyiv city council said on social media.

It said the video falsely claimed there were military personnel in the facilities, one of which is a children's hospital.

Russia's forces have previously struck medical facilities close to the front lines during the war, now in its third year.

In March 2022, Russia bombed a maternity hospital in the southern city of Mariupol, in what Kyiv and Western officials have called a war crime.

Officials on both sides of the front lines said at least five people died on Friday from the latest wave of cross-border strikes.

Ukraine's interior ministry said two women, aged 77 and 69, were killed by Russian shelling on the town of Bilopillya in the northeastern Sumy region.

The Russian governor of the Kursk region, which borders Ukraine, said one person died in a Ukrainian shelling attack on Friday.

In the Bryansk region, another Russian border area, a person injured a day earlier in a Ukrainian drone attack succumbed to her wounds, the governor said.

Moscow-installed authorities also said one person was killed in an attack on the Lugansk region, one of the four Ukrainian regions that Russia claims to have annexed.

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