Russia on Monday claimed its deadly missile attack on Ukraine's Sumy that killed and wounded scores including children had targeted a gathering of Ukrainian troops, while European leaders condemned the attack as a war crime.

NATO Secretary-General Mark Rutte said he had visited the southern Ukrainian city of Odesa with President Volodymyr Zelenskiy on Tuesday and declared NATO's support for Ukraine was unwavering. Rutte's visit was a show of solidarity with Kyiv following a Russian missile strike on the northern city of Sumy on Sunday that killed 35 people and wounded more than 100.

NATO’s support for Ukraine remains “unwavering,” the alliance’s secretary-general said Tuesday, emphasizing that more than 20 billion euros — over $22 billion — in security assistance has already been pledged by NATO allies in the first three months of the year.