French striker Yaya Sanogo scored four times as Arsenal crushed Portuguese champions Benfica 5-1 at the Emirates Cup friendly tournament in London yesterday.

The 21-year-old, who has never scored a competitive goal for the club, claimed a first-half hat-trick and added another goal in the second half to upstage star signing Alexis Sanchez, who made his first appearance as a late substitute.

Costa Rica forward Joel Campbell, back at Arsenal after three seasons out on loan, scored the hosts’ other goal, with Nicolas Gaitan replying for Europa League runnersup Benfica.

Sanogo broke the deadlock in the 26th minute with a clever backheeled finish from Aaron Ramsey’s right-wing cross.

Hector Bellerin then teed up Campbell to bludgeon home a leftfoot volley in the 40th minute.

Improbably, there was time for Sanogo to complete his hat-trick. He tucked away a volleyed cross from Campbell in the 44th minute and then flicked in a centre from Kieran Gibbs at the second attempt in stoppage time.

The towering former Auxerre striker claimed his fourth four minutes into the second period, rolling the ball into an empty net after Benfica goalkeeper Moraes Artur had parried from Ramsey.

Nicolas Gaitan headed in from a long throw-in with just under half an hour remaining but Arsenal were already out of reach.