U.S. President Donald Trump has said his Russian counterpart, Vladimir Putin, is "probably" involved in assassinations and poisonings.

Asked by a CBS News' 60 Minutes host, why he never harshly commented on Putin's actions, Trump said: "I think I'm very tough with him personally. I had a meeting with him. The two of us. It was a very tough meeting and it was a very good meeting."

Asked directly whether he believes Vladimir Putin is involved in assassinations and poisonings, Trump said: "Probably, he is, yeah, probably."

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The U.S. president also admitted he believed Russia meddled in the 2016 U.S. elections, although adding that "China meddled, too."

Speaking on the Ukraine issue, Donald Trump boasted that he was the one who "gave Ukraine offensive weapons and tank killers."

"Obama didn't. You know what he sent? He sent pillows and blankets," Trump said. "He's the one who gave away part of Ukraine where Russia has now submarines."