Ukraine's top prosecutor has called for the International Criminal Court to prosecute Russia over a missile strike on a children's hospital in Kyiv earlier this week.

Ukraine's capital suffered on Monday one of its worst days of airstrikes since the start of Russia's war, and attacks across the country killed at least 44 people including two adults at Okhmatdyt children's hospital, Ukrainian officials have said.

"For the sake of international justice, cases like the intentional attack on the biggest child hospital in Kyiv (are) worth lifting to the ICC," Prosecutor General Andriy Kostin told Reuters late on Thursday in an interview in The Hague, where the ICC is based.

Moscow denies attacking the hospital and has blamed Ukrainian anti-missile fire for the hit on the clinic, which is one of Europe's largest and treats patients with serious conditions such as cancer and kidney disease.

A U.N. rights mission has said there is a "high likelihood" the hospital took a direct hit from a Russian missile, and Ukraine's security service said it had unequivocal evidence the medical facility was hit by a Russian Kh-101 cruise missile.

Kostin, in The Hague for regular meetings with legal officials, said if the ICC took on the prosecution of the hospital strike, it could help establish a pattern of attacks that show Russia is committing crimes against humanity in Ukraine.

The ICC's Office of the Prosecutor said on Tuesday one of its teams had visited the site of the hospital strike. While the ICC does not publicly comment on which indictments it is investigating, it has warned that anyone deemed responsible for attacking civilian sites could be prosecuted.

It has issued six arrest warrants for alleged Russian crimes in Ukraine including one against President Vladimir Putin.

Moscow has repeatedly denied accusations that its forces have committed atrocities since it invaded its neighbour.

Kostin said the decision to prosecute lies with the ICC's prosecutor, adding that Ukraine was ready to share any physical evidence or details of its investigation with the court.

He said that while Ukrainian authorities were looking into all of Monday's attacks, they can only bring charges of war crimes and not the more serious offence of crimes against humanity because they are not part of Ukraine's criminal code.

A key element of prosecutions for crimes against humanity involves demonstrating systematic attacks on civilians, Kostin said.

"It's important to show that Russia itself, at the moment, is a criminal state," he said.