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

Ukraine claimed Saturday that its intelligence indicates Russian forces are currently regrouping in eastern Ukraine, then the tankers intend to move toward Kharkiv, Ukraine's Defense Intelligence Chief Kyrylo Budanov said.

Russians are also regrouping in the direction of Izum, in the Kharkiv region, the Ukrainians said.

"They plan to enter Kharkiv in the first place. They will try to conquer the city of Mariupol and only after that they can try to initiate Kiev," Budanov said in an interview on CNN.

To compensate for their significant losses in Ukraine, the Russian army is transferring additional troops to Belgorod (Russia), from where they are relocated to Kharkiv region, the Ukrainians claimed.

Budanov said Ukraine needs serious military support from allies so its soldiers can more effectively resist Russian aggression.

-ABC News' Mike Trew

Ukrainian President Volodymyr Zelenskyy called Friday's deadly missile attack on the Kramatorsk train station in eastern Ukraine "another war crime of Russia."

"All the world's leading powers have already condemned Russia's attack on Kramatorsk," Zelenskyy said during his latest national address Friday. "We expect a firm, global response to this war crime."

The president called for the missile strike, which killed at least 50, to be among the charges in a war crimes tribunal against Russia.

"All the efforts of the world will be aimed to establish every minute: who did what, who gave orders. Where did the rocket come from, who was carrying it, who gave the order and how the strike was coordinated," Zelenskyy said. "Responsibility is inevitable."

During his daily press briefing, Pentagon spokesman John Kirby was clear that the U.S. believes that Russia was behind the rocket attack on a train station in eastern Ukraine earlier Friday.

"We find unconvincing Russian claims that they weren't involved, particularly when the ministry actually announced it and then when they saw reports of civilian casualties they decided to unannounce it,” Kirby said during Friday afternoon's briefing. "So our assessment is that this was a Russian strike and they used a short-range ballistic missile to conduct it."

Kirby called it a part of the trend by Russia of "brutality" and "carelessness" in not avoiding civilian casualties as they carry out this war in Ukraine.

At least 50 people, including five children, were killed in the rocket attack in Kramatorsk, Ukrainian authorities said.

A Kremlin spokesman denied involvement in the attack, saying Russia's Armed Forces do not use the type of missile used in the strike and that no combat tasks were planned in the region.

-ABC News' Luis Martinez

European Union President Ursula Von der Leyen was seen on camera witnessing a mass grave in Bucha, Ukraine, during a visit to the demolished city with the EU's chief diplomat Josep Borrell and Ukrainian Prime Minister Denys Shmyhal.

After touring Bucha, Von der Leyen met with Ukrainian President Volodymyr Zelenskyy and handed him an envelope with a questionnaire, marking the first step toward membership in the EU. Zelenskyy said he'd have responses in one week.

Global officials have accused Russian troops of committing war crimes after graphic images emerged of civilians lying dead in the streets of Bucha following the withdrawal of Russian forces.

At a press conference Thursday Secretary of State Antony Blinken said, "The sickening images and accounts coming out of Bucha and other parts of Ukraine have only strengthened our collective resolve and unity."