Arsenal’s Pierre-Emerick Aubameyang struck a vital late goal to seal a 3-1 win over Valencia and give his side breathing space for the second leg of its Europa League semi-final in Spain next week.

Alexandre Lacazette scored twice in the first half after Mouctar Diakhaby stunned the Emirates crowd with an early header which gave Valencia the lead. The tie was still balanced on a knife edge, however, before striker Aubameyang’s 90th minute volley put his side in control ahead of the return leg in Mestalla.

Unai Emery’s team will need to show more steel if it is to reach the final in Baku. London rival Chelsea drew 1-1 away in the first leg of its last four round against Eintracht Frankfurt. Valencia sliced through the home defence at will and had gone close to scoring before Frenchman Diakhaby put it ahead.

When a corner was swung over in the 11th minute, an unmarked Rodrigo headed it back across goal where Diakhaby rose above three stationary Arsenal defenders to nod past Petr Cech. For a while, there was panic in the Arsenal ranks and both Daniel Parejo and Goncalo Guedes threatened a second.

But Lacazette stopped Valencia in its tracks seven minutes after the host went behind. He released Aubameyang with a superb pass before arriving in the box to steer a shot past Neto after his fellow striker cleverly held up the ball before squaring it. Seven minutes later, Granit Xhaka’s cross found Lacazette and his downward header had just enough power to cross the line despite Neto’s desperate attempt to keep it out. Suddenly Arsenal was rampant and another Xhaka cross found Aubameyang but he bounced his volley over.

Valencia burst back into life in the second half and it needed a brave header by Arsenal captain Laurent Koscielny to stop a cross reaching the dangerous Guedes. Lacazette wasted two gilt-edged chances to put the home side in control, miscuing a header from Aubameyang’s cross with the goal gaping and weakly shooting straight at Neto. Valencia would have been reasonably content heading back to Spain with a one-goal deficit, but it switched off in the dying minutes. Moments after Neto made a superb save, Arsenal kept the ball alive and Sead Kolasinac’s cross found Aubameyang at the far post, with the forward driving the volley home.