"Our musicians wear body armour instead of tuxedos," he was quoted as saying by BBC.

"They sing to the wounded in hospitals, even to those who can't hear them. But the music will break through," he said.

"Support us in any way you can, but not with your silence," he continued. "Fill the silence with music."

The President's pre-taped message was played ahead of the  performance by John Legend.

John was joined on-stage  by Ukrainian musicians Mika Newton and Suzanna Iglidan.