West Ham, who made the Europa League semi-finals last season, went into the game after back-to-back losses in the Premier League to Manchester City and Nottingham Forest.

But Italian international Scamacca, signed for £30 million from Sassuolo, eased the nerves by finding the target in the 23rd minute after being teed up by another new signing, Maxwel Cornet.

Jarrod Bowen added a second in the 64th minute before Viborg pulled one back through Jakob Bonde five minutes later.

Twelve minutes from time, substitute Michail Antonio scored a third for West Ham to put the Londoners on course for a place in the group stage.

Villarreal, who were Europa League champions in 2021, overcame an early shock to defeat Hajduk Split 4-2.

Stipe Biuk gave Hajduk a second-minute lead but the Spanish side quickly recovered and were 4-1 ahead by the break.

Jose Luis Morales, with a brace, a Marko Livaja own goal and a Gerard Moreno strike in first-half stoppage time put Villarreal in charge.

A Marco Fossati penalty five minutes from time, however, gave Hajduk a glimmer of hope of overturning the deficit in next week's second leg.

Anderlecht, 32-time Belgian champions, came away from Young Boys in Switzerland with a 1-0 win secured by a Hannes Delcroix goal just before the hour mark.

Former Arsenal star Mesut Ozil was left on the bench as his Turkish side Basaksehir were held 1-1 by Antwerp in Istanbul.