Following situation occurred in my last tournament:
It was a 5 min blitz game without time increment. My opponent didn't have any material left.
I touched my rook and wanted to place it on the backrank to deliver check mate in this move.
While I am moving my rook, my opponent claims a draw because my flag on the chessclock has fallen.
Nevertheless I moved my rook and announced checkmate. Then I saw both flags have fallen.
Then the arbiter arrived at the board and gave me the point because he said he sees a checkmate.
Is it valid for my opponent to claim a draw, even if it's not his move? What would be the correct way for my opponent to claim a draw?