Olivier Giroud scored twice from the bench as Arsenal went top of the Premier League and extended Sunderland's miserable start to the season.

The Frenchman volleyed in with his first touch to restore Arsenal's lead after a Jermain Defoe penalty cancelled out Alexis Sanchez's headed opener.

Arsenal had looked in real danger of dropping points against the bottom side when Defoe finished coolly from the spot after Petr Cech upended Duncan Watmore on 65 minutes.

But Giroud's first goal was swiftly followed by a headed second, before Sanchez completed a flurry of three goals in seven minutes.

The win moved Arsenal top of the Premier League ahead of Manchester City and Liverpool's games.

Defeat will see pressure on David Moyes intensify - Sunderland are still winless with just two points from their first 10 games.