The Hammers started the second half brightly but were undone when Leandro Trossard latched on to Pascal Gross's flick to inflict a third straight league defeat on the hosts.

Afterwards, Hammers boss David Moyes said he was "concerned" by his side's start to the campaign.

"We've not quite got everything in place," he said. "Hopefully our quality will show through in the coming weeks."

To say alarm bells were ringing would be "too strong", Moyes added. "We finished seventh, then sixth, and we take positives from that. We've lost a wee bit. We need to get away from that position.

"Last year we were one of the top goalscorers. But we are struggling a bit for goals. We're aware we are not as free-flowing as we have been.

"I am concerned, but also I'm having to bed people in."

West Ham have now had 38 shots in their opening three league games without scoring a goal.

They had their chances on Sunday, but Aaron Cresswell's fierce effort was well blocked by Joel Veltman, before Robert Sanchez produced two acrobatic saves late on to keep out two Tomas Soucek headers.

Meanwhile, Brighton have equalled their longest unbeaten run in the top flight at eight games, stretching back to the end of last season.

The Seagulls have moved up to fourth this term, while the Hammers are rooted to the foot of the table after losing their first three games without scoring for only the second time in their history.

Clinical Seagulls expose Hammers' shortcomings

Both sides came into the game in contrasting form, with Brighton having beaten Manchester United and sharing the points with Newcastle, while West Ham had not been able to get going in the league.

Boosted by their midweek win over Danish side Viborg in their Europa Conference League play-off first leg, the hosts started on the front foot and could have taken an early lead when Said Benrahma cut in on his right foot before firing wide.

But the first goal came for the visitors after the impressive Welbeck introduced Kehrer to the speed of the Premier League by forcing the German defender into a mis-timed last-ditch tackle.

The incident had to be checked to determine whether it was inside the area, but referee Anthony Taylor's original decision stood and Mac Allister made no mistake from the spot.

Brighton were able to show the clinical edge that the Hammers are lacking, with lone striker Michail Antonio cutting an isolated figure for the 75 minutes he was on the field.

He had the lowest number of touches of any player who started the game (21), including both goalkeepers, and is a shell of his imposing best from the start of last season, when he scored four goals in his opening three league games.

With clear chances at a premium at both ends, Brighton cut through decisively as Gross managed to turn the ball around the corner for Trossard to run clear and beat Lukasz Fabianski with a neat finish.

West Ham will have to improve their sharpness in front of goal if they are to repeat the success of last year, while seven points from a possible nine for Brighton is just reward for a brilliant start to the new campaign.