Pierre-Emerick Aubameyang scored a debut goal and Aaron Ramsey his first hat-trick as Arsenal thumped a disorganised Everton.

Aubameyang, a club-record £56m signing from Borussia Dortmund on Wednesday, chipped in from fellow new arrival Henrikh Mkhitaryan's pass as the home side led 4-0 by half-time.

Television replays showed the goal should have been ruled out for offside, although the visitors could hardly claim the decision made a huge difference to the match.

Everton conceded three times in the opening 20 minutes amid defensive chaos, with Ramsey touching in the opener from Mkhitaryan's cross.

Laurent Koscielny got in front of Aubameyang to head the second at the far post after Shkodran Mustafi glanced on Mesut Ozil's corner before Ramsey scored a deflected third.

Aubameyang struck the fourth before half-time, prompting Everton manager Sam Allardyce to abandon his three-man central defence and revert to a back four.

Substitute Dominic Calvert-Lewin headed an Everton consolation from Cuco Martina's left-wing delivery before Ramsey swept in his hat-trick goal from another low Mkhitaryan cross.

However, Arsenal lost goalkeeper Petr Cech to a calf injury in a collision with Oumar Niasse as the striker hit the post in the second half.