Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

The death toll climbed to 57 on Sunday from an alleged Russian rocket attack Friday on a crowded train station in the eastern Ukrainian city of Kramatorsk, Ukrainian officials said.

Among those killed in the attack were five children, said Pavlo Kyrylenko, governor of the Donetsk Oblast in the Donbas region. Another 109 people were wounded when two Russian rockets struck the train station.

"There are many people in a serious condition, without arms or legs," said Kramatorsk Mayor Oleksandr Goncharenko according to the Associated Press.

The number of dead victims in the attack grew from 50 on Friday, officials said.

Ukraine's state-owned railway company issued a statement on Facebook calling the attack "a purposeful strike on the passenger infrastructure of the railway and the residents of the city of Kramatorsk."

Graphic images provided by Ukrainian officials showed the aftermath of the attack -- bodies lying on the ground next to scattered luggage and debris, with charred vehicles parked nearby.

The remnants of a large rocket with the Russian words painted on its side reading "for our children" was also seen on the ground next to the main building of the train station.

Russia has denied involvement in the attack. Kremlin spokesman Dmitry Peskov claimed involvement of Russian forces was already ruled out by the Russian Ministry of Defense, based on the type of missile that was used -- a Tochka-U short-range ballistic missile.

"Our armed forces do not use missiles of this type," Peskov told reporters during a press briefing Friday. "No combat tasks were set or planned for today in Kramatorsk."

U.S. Defense Secretary Lloyd Austin met on Sunday via videoconference with a small group of Ukrainian troops who have been training in the United State since before Russia invaded their country on Feb. 24, according to Pentagon press secretary John Kirby.

Austin spoke to Ukrainian soldiers as the group prepared to head back to Ukraine on Sunday.

"The Secretary thanked them for their service and for their courage, noting the skill with which the Ukrainian Armed Forces are fighting Russia's unprovoked invasion," Kirby said in a statement. "And he (Austin) pledged continued U.S. support for providing and coordinating additional security assistance."

The Ukrainians soldiers were in Biloxi, Mississippi, for naval training when the invasion began on Feb. 24. While in the United States, the U.S. Defense Department also trained the soldiers on how to use equipment the United States is sending as part of its military assistance to Ukraine, including Switchblade drones, Kirby said.

Kirby said the group spoke to Austin on Sunday from in Little Creek, Virginia, where they are "completing additional advanced tactical training."

-ABC News' Matt Seyler

Austrian Chancellor Karl Nehammer confirmed he plans to travel to Moscow on Monday and meet with Russian President Vladimir Putin.

Nehammer noted in a Twitter post on Sunday that while Austria is militarily neutral, the country's position on Russia's war against Ukraine is that it must stop.

Nehammer said that humanitarian corridors and a ceasefire need to be established and that a full investigation should take place appraising allegations of war crimes committed by Russia in Ukraine.

The chancellor said he has notified Ukrainian President Volodymyr Zelenskyy and his European partners of his plan to meet with Putin.

Nehammer's decision to meet with Putin comes after he visited Kyiv on Saturday and met with Zelenskyy.

-ABC News' Christine Theodorou

A top Ukrainian prosecutor said the bodies of more than 1,200 Ukrainians allegedly killed by Russian forces have been found in or near the capital of Kyiv since the start of the Russian invasion in February.

Ukraine's prosecutor-general, Iryna Venediktova. made the grim announcement on Sunday, the 46th day of the war in Ukraine.

"As of the morning of April 10, we found the bodies of 1,222 people who died during the Russian occupation of Kyiv region. This is only in Kyiv region," Venediktova said.

Venediktova said many of the bodies recovered in the Kyiv region are those of civilians.

"Of course, what we have seen on the ground in all regions of Ukraine are war crimes, crimes against humanity and we will do everything to prosecute them," Venediktova said.

In addition to the atrocities found near the capital city, Venediktova mention at rocket attack Friday on a train station in Kramatorsk in the Donetsk Oblast of eastern Ukraine that killed 50 people, including five children. Venediktova called the deadly attack in Kramatorsk a "war crime."