Washington: Former US President Donald Trump on Sunday labelled Russian President Vladimir Putin "crazy" for launching a wave of deadly attacks across Ukrainian cities, warning that a full takeover attempt of Ukraine would “lead to the downfall of Russia.”

“I've always had a very good relationship with Vladimir Putin of Russia, but something has happened to him. He has gone absolutely CRAZY!” Trump posted on Truth Social. “I’ve always said that he wants ALL of Ukraine, not just a piece of it, and maybe that’s proving to be right. But if he does, it will lead to the downfall of Russia!”

The comments came after Russia unleashed a record number of drone strikes across Ukraine, killing at least 13 people, including two children aged eight and twelve, and a 17-year-old in the northwestern region of Zhytomyr, according to Ukrainian officials.

Speaking to reporters on the tarmac at Morristown airport before boarding Air Force One, Trump expressed frustration with the Russian president's actions. “I’m not happy with what Putin is doing. He’s killing a lot of people, and I don’t know what the hell happened to Putin,” he said. “I’ve known him a long time, always got along with him, but he’s sending rockets into cities and killing people — and I don’t like it at all.”

Trump, who has in the past expressed admiration for Putin, has recently voiced growing dissatisfaction with Moscow’s stance in the stalled truce negotiations with Kyiv. When asked if he would consider increasing US sanctions on Russia in response to the latest violence, Trump said he “absolutely” would.

His remarks contrast with US Secretary of State Marco Rubio’s testimony to Congress earlier in the week, in which Rubio claimed that Trump believed threatening new sanctions at this time could derail diplomatic talks.

The deadly strikes coincided with the largest prisoner swap between Russia and Ukraine since the full-scale invasion began in February 2022, with both sides reportedly exchanging 1,000 soldiers and civilian prisoners.

Ukrainian President Volodymyr Zelensky condemned the attacks and reiterated the need for stronger international action. “Without truly strong pressure on the Russian leadership, this brutality cannot be stopped,” he said on social media.

Trump and Putin reportedly held a two-hour phone call on Monday, after which Trump announced that Moscow and Kyiv would “immediately start negotiations towards a ceasefire.” However, no such commitment has been publicly confirmed by the Kremlin, which instead floated a vague proposal to develop a “memorandum” outlining its demands for peace.