The Burkina Faso international nodded Ajax ahead after 25 minutes at the Amsterdam Arena before Danish teenager Kasper Dolberg rifled in a second from Traore's towering header.

Amin Younes struck just after half-time as Ajax tormented the visiting defence and although Mathieu Valbuena pulled a goal back for Lyon, Traore capped a convincing win with the hosts' fourth on 71 minutes.

Lyon brought on leading scorer Alexandre Lacazette, who was only fit enough to come off the bench after nursing a hamstring injury, for the final quarter hour, but Ajax are clear favourites to reach the final in Stockholm on May 24.

The Dutch giants are seeking a first appearance in a European final since losing to Juventus on penalties in the 1996 Champions League showpiece, with Lyon facing a monumental task to turn the tie around in next Thursday's return leg in France.

Three-time European champions Manchester United travel to Celta Vigo of Spain in Thursday's second semi-final. Jose Mourinho has confirmed that Paul Pogba, Eric Bailly and Juan Mata will all be available after injury.