West Ham have come from behind to beat AZ Alkmaar 2-1 in their first-leg Europa Conference League semi-final on a tough night for Socceroos No.1 Mat Ryan in London.

The hero of the penalty shootout win over Anderlecht in their quarter-final, Alkmaar keeper Ryan was culpable for both Hammers goals that kept the London club's dreams of a first trophy in 43 years alive.

David Moyes's men were big favourites to beat the Dutch dark horses, but were put on the back foot at a sold-out London Stadium when goalkeeper Alphonse Areola gifted AZ the lead before half-time.

But another goalkeeping error this time from Ryan gave West Ham a penalty which Said Benrahma converted.

Antonio then prodded home from a corner after a goalmouth scramble to give the Hammers a crucial lead going into next Thursday's second leg in the Netherlands.

West Ham are now a step closer to a final in Prague on June 7 against Fiorentina or Basel, the latter also winning their first-leg tie 2-1.

Ominously, Ryan was unbeaten in his five previous matches against West Ham during his spell at Brighton and he set about trying to maintain that record when he got down well to tip Benrahma's curler behind.

The hosts got an early warning when former Southampton midfielder Jordy Clasie fizzed a low shot just past the post.

AZ then took a shock lead five minutes before half-time, Areola letting Tijjani Reijnders' shot in at his near post.

It was not a gaffe on the scale of the one West Ham benefitted from in their win over Manchester United on Sunday, when David de Gea let Benrahma's tame shot roll in, but it was still not a good look for the Hammers' Cup keeper.

West Ham protested that there had been a foul on Lucas Paqueta in the build-up - Turkish referee Halil Umut Meler even put the whistle to his lips before opting to play on - but the goal stood.

But the Hammers were thrown a lifeline in the 67th minute when Ryan missed his punch at a corner and caught Jarrod Bowen square in the face.

Meler, who had infuriated the home crowd all match, pointed to the penalty spot and Benrahma stepped up to bury a perfect spot-kick just inside the post.

Eight minutes later West Ham forced the win after more uncertainty from Ryan from a corner as he failed to come off his line and allowed Rice to chip the ball into the danger zone where Nayef Aguerd's header was cleared off the line by Yukinari Sugawara, only for Michail Antonio to poke the rebound into the net.

"We've got a narrow lead but nothing more than that," said Moyes.

"The tie is very evenly balanced, there is very little in the game, if we were losing by a goal I wouldn't be saying we were out of the tie.

"We're just off a big win against Manchester United and just won 2-1 in a semi-final first leg, so that's OK. But we have a big job to do next week."

In Italy, Zeki Amdouni struck in stoppage time as Basel won 2-1 at Fiorentina.

Arthur Cabral headed the Italians in front from a corner in the 25th minute.

Basel, though, were back on level terms with 20 minutes left through a fine individual effort from Andy Diouf before Amdouni completed the turnaround when he slotted in what could prove a crucial second goal following a free-kick.