Russian strikes kill 23 as Zelensky urges 'special tribunal' for Moscow

Russian missiles struck Vinnytsia in central Ukraine Thursday, killing at least 23 people including three children, in what President Volodymyr Zelensky called "an open act of terrorism".

The midday attack on the city hundreds of kilometres from the frontlines and invading Russian troops came as EU officials convened in The Hague to discuss war crimes in Ukraine.

The charred remains of upturned cars surrounded by burnt debris were seen in images distributed by officials next to a business gutted by a fire with brown smoke billowing nearby.

"There were eight rockets, two of which hit the centre of the city. Twenty people have died, including three children. There is a large, large number of wounded," Zelensky said during an address to European officials at The Hague.

Rescuers later updated the death toll to 23, saying the search for another 39 people continues.

UN Secretary-General Antonio Guterres said he was "appalled" by the attack and called for accountability for such assaults on civilians.

And Zelensky led a moment of silence before urging European and International Criminal Court officials to open a "special tribunal" into Russia's invasion.

"I believe it is inevitable that International Criminal Court will bring accountability to those guilty of crimes under its jurisdiction: war crimes, crimes against humanity, genocide."

The ICC in The Hague opened an investigation into possible war crimes in Ukraine just days after Moscow's forces invaded and it dispatched dozens of investigators to the country to gather evidence.

Russia invaded on February 24 and the conflict has seen thousands of people killed, destroyed cities and forced millions to flee their homes.

"Every day, Russia kills civilians, kills Ukrainian children, carries out missile attacks on the civilian facilities where there is no military target. What is this, if not an open act of terrorism?" Zelensky said after the Vinnytsia attack.

A Ukraine military spokesman said its forces had managed to knock out two from a barrage of cruise missiles that were launched from a Russian submarine in the Black Sea and caused widespread damage in Vinnytsia.

Deadly strikes in central Ukraine have become relatively rare, but the war has raged around cities like Mykolaiv in the south which the presidency said was hit by a "massive missile strike".

"Two schools, transport infrastructure and a hotel were damaged," the presidency said in its morning military update Thursday.

The skeletal insides of one building gutted by the strikes were visible in images distributed by local officials, with municipal workers clearing bricks and rubble strewn after the attack.

The heaviest fighting in Ukraine, however, has focused recently on the industrial Donbas region in the east.

Moscow-backed troops there said Thursday they were closing in on their next target, after wresting control of sister cities Lysychansk and Severodonetsk two weeks ago.

"Siversk is under our operational control, which means that the enemy can be hit by our aimed fire all over the area," a pro-Moscow rebel official, Daniil Bezsonov, was cited as saying by Russian state-run news agency TASS.