'We must stop the aggressor,' Zelenskyy tells Biden

Ukraine's President Volodymyr Zelenskyy called Tuesday for "aggressor" Russia to be stopped as he spoke by phone with US President Joe Biden about Moscow's invasion.

"Just had a conversation with the US President. The American leadership on anti-Russian sanctions and defence assistance to Ukraine was discussed," Zelenskyy said on Twitter.

"We must stop the aggressor as soon as possible."

The White House said the leaders spoke for just over 30 minutes and discussed Russia's increasing strikes on civilian sites, including Tuesday's bombing of Kyiv's main television tower near the Babi Yar Holocaust memorial.

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More than 30,000 Jews were slaughtered by the Nazis during World War II in the Babi Yar ravine.

The tragedy is commemorated by a memorial statue and is a site of pilgrimage for many Jews.

Five people were killed in Tuesday's bombing, and Ukrainian officials accused Moscow of threatening the memorial.

The phone call came on day six of Russia's invasion of Ukraine, with violence escalating in Kyiv and the eastern city of Kharkiv.

"President Biden underscored the United States' sustained help for Ukraine, including ongoing deliveries of security assistance, economic support, and humanitarian aid," the White House said.