KYIV, May 25 (Reuters) - Russian forces launched a barrage of 367 drones and missiles at Ukrainian cities overnight, including the capital Kyiv, in the largest aerial attack of the war so far, killing at least 12 people and injuring dozens more, officials said.

The dead included three children in the northern region of Zhytomyr, local officials there said.

Ukrainian President Volodymyr Zelenskiy called on the United States, which has taken a softer public line on Russia and its leader, Vladimir Putin, since President Donald Trump took office, to speak out.

"The silence of America, the silence of others in the world only encourages Putin," he wrote on Telegram.

"Every such terrorist Russian strike is reason enough for new sanctions against Russia."

Trump later responded in terms critical of Putin.

"I'm not happy with what Putin's doing. He's killing a lot of people," Trump told reporters in New Jersey on Sunday just before boarding his plane for a return to the White House from his Bedminister golf club.

"I don't know what the hell happened to Putin. I've known him a long time. Always gotten along with him. But he's sending rockets into cities and killing people, and I don't like it at all. We're in the middle of talking and he's shooting rockets into Kyiv and other cities," Trump said.

Asked if he was considering more sanctions on Russia, Trump said, "Absolutely."

Upon returning to Washington, Trump posted more comments on social media, saying of Putin, "He has gone absolutely CRAZY!"

Trump also criticised Zelenskiy, posting that the Ukrainian leader "is doing his Country no favors by talking the way he does. Everything out of his mouth causes problems, I don't like it, and it better stop."

The Russian attack was the largest of the war in terms of weapons fired, although other strikes have killed more people.

Interior Minister Ihor Klymenko said 12 people had been killed and 60 more wounded. Earlier death tolls given separately by regional authorities and rescuers had put the number of dead at 13.

"This was a combined, ruthless strike aimed at civilians. The enemy once again showed that its goal is fear and death," he wrote on Telegram.

The assault comes as Ukraine and Russia prepared to conduct the third and final day of a prisoner swap in which both sides will exchange a total of 1000 people each.

U.S. Special Envoy to Ukraine Keith Kellogg said on Sunday the attack was "a clear violation" of the 1977 Geneva Peace Protocols and called for an immediate ceasefire.

Photo from Reuters