West Ham United have come from behind to beat AZ Alkmaar 2-1 in the first leg of their Europa Conference League semi-final at the London Stadium on Thursday night.

Tijjani Reijnders opened the scoring for the visitors with a long-range effort on the stroke of half time, and the Hammers were at risk of seeing their 12-game unbeaten run in the competition come to an end.

However, second-half strikes from Said Benrahma and Michail Antonio turned the tie on its head to ensure that David Moyes's men take a one-goal advantage into next week's second leg in the Netherlands.

In front of a fired-up London Stadium crowd, the first chance of the night fell to West Ham forward Jarrod Bowen, who could only direct a header over the crossbar after leaping above the Alkmaar backline to meet a teasing cross from Declan Rice.

Benrahma was a bright spark for the Hammers throughout the contest and the Algerian came close to opening to scoring inside the first 12 minutes, but his first-time effort from the edge of the area was brilliantly tipped round the post by former Brighton & Hove Albion and Arsenal goalkeeper Mat Ryan.

Alkmaar had their fair share of possession and were content to sit back, patiently pass the ball out from the back inside their own half before slowly encroaching the final third, but Pascal Jansen's men rarely threatened in the final third.

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However, the visitors managed to break the deadlock with their first decent effort on goal in the 41st minute when Reijnders blasted a 30-yard strike under the gloves of Alphonse Areola, who should have done better to keep out the shot at his near post.

West Ham felt that Lucas Paqueta was pushed in the back before Alkmaar won back possession and broke on the counter-attack, but VAR opted against intervening and the goal was allowed to stand.

With frustrations growing inside the London Stadium, an increase in tempo and a greater sense of urgency was required from West Ham in the second half, but they initially struggled to get going and Alkmaar were able to control the game in possession.

The Hammers had to wait until the hour mark for their first real chance in the second half when Bowen received the ball on the right flank and cut inside before firing a left-footed strike wide of the near post.

However, West Ham were presented with a route back into the tie just four minutes later when the referee awarded a penalty to the hosts after Ryan caught the head of Bowen with his fist inside the six-yard box.

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Ryan saved two penalties in Alkmaar's shootout triumph over Anderlecht in the previous round, but the Australian was unable to keep out Benrahma's powerful effort from 12 yards, with the Hammers winger blasting his strike into the bottom-left corner to restore parity.

West Ham then completed the turnaround on the 75-minute mark when Antonio prodded the ball home from just a few yards out after Nayef Aguerd initially saw his headed effort cleared off the line by Yukinari Sugawara.

Antonio was replaced by Danny Ings soon after, and the latter linked up well with Benrahma down the left before the Algerian placed a side-footed effort high and wide over the crossbar.

Bowen then fizzed a dangerous delivery across the face of goal, but no Hammers attackers were prepared to bust a gut to connect with the cross inside the six-yard area.

On a night filled with nerves and frustration, West Ham managed to battled their way back into the tie and get the job done to gain a first-leg advantage, and they know that at least a draw in the second leg will be enough to send them through to their first European final in 40 years.

In the other Europa Conference League semi-final, Basel have come from behind to beat Fiorentina 2-1 in Italy, with Zeki Amdouni netting a dramatic 92nd-minute winner to give the Swiss outfit a first-leg advantage.

West Ham now turn their attention back to the Premier League with a trip to Brentford on Sunday, while AZ Alkmaar play host to FC Emmen in the Eredivisie.