It took the Belgian's tally to four goals in two games after he netted a brace in Wednesday's 3-1 win at Crystal Palace, with playmaker Andreas Pereira grabbing the other for the hosts in a rip-roaring clash at Old Trafford.

Southampton took the lead against the run of play in the 26th minute when 20-year-old French wing-back Yan Valerie unleashed a thunderbolt from 25 metres which beat United's stunned keeper David De Gea at the near post.

Having missed a host of first-half chances, the home side equalised in the 53rd minute as the lively Pereira teed himself up for a long-range shot and curled it brilliantly past Saints keeper Angus Gunn.

Six minutes later, Pereira released Lukaku with fine footwork and the striker side-stepped a defender before he drilled a low shot with his weaker right foot into the bottom left corner of the net.

James Ward-Prowse appeared to have snatched a point for the Saints with a stunning free kick from 25 metres before Lukaku powered in another right-foot shot in the 89th minute and Paul Pogba missed a stoppage-time penalty for United who climbed to fourth in the table, one point ahead of Arsenal.