The 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 back rank to deliver checkmate on this move. While I am moved my rook, my opponent claimed a draw because my flag on the chess clock has fallen Nevertheless, I moved my rook and announced a 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?