SUMY, Ukraine/KYIV, April 13 (Reuters) - Two Russian ballistic missiles slammed into the heart of the northern Ukrainian city of Sumy on Sunday, killing 34 people and wounding 117 in the deadliest strike on Ukraine this year, officials said.

President Volodymyr Zelenskiy demanded a tough international response against Moscow over the attack, which came with U.S. President Donald Trump's push to rapidly end the war struggling to make a breakthrough.

The leaders of Britain, Germany and Italy condemned the attack.

Trump, when asked about the Russian strike, said that it was terrible. "And I was told they made a mistake," he said without elaborating further. "But I think it's a horrible thing."