In the penultimate match at the Boleyn ahead of West Ham's summer move to the Olympic Stadium, the home team was repeatedly punished for defensive lapses, and Swansea was two goals up within half an hour thanks to winger Wayne Routledge and striker Andrew Ayew.

Midfielder Ki Sung-Yueng netted Swansea's third in the 50th, and although Stephen Kingsley gave one back to West Ham from an own goal, substitute Bafetimbi Gomis completed the rout in second-half injury time.

West Ham thus fell to an unexpected third home loss this season, and first home loss to Swansea since 1956.

West Ham stayed sixth in the league, four points and one place behind Manchester United, whom it plays on Tuesday in the last ever match at Upton Park after 112 years at the Boleyn ground.

"I am steaming, I'm not only disappointed, I'm angry. But after the game it's not the time to fume, you have to be positive, you have to react," West Ham manager Slaven Bilic said.

"We've done wrong, but we have an opportunity in three days to put it right in the most special game at Upton Park, the last game."

Swansea, a team in freefall up until the January arrival of Italian head coach Francesco Guidolin, climbed from 13th to 11th in the league, fielding a makeshift side that outgunned an under-par West Ham side fighting for a spot in Europe next seaon.

Despite resting the likes of Wales and club captain Ashley Williams and Icelander Gylfi Sigurdsson ahead of Euro 2016, Swansea was sharp and clinical, taking advantage of naive West Ham defending on the flanks. The home team was also wasteful in front of goal and rarely found striker Andy Carroll.

Guidolin, who said he couldn't confirm whether he'd still be at the helm of the south Wales side next season, said he was proud of his team's performance.

"Now we can say it was for us a season that has been difficult, but now we have the possibility to finish well, and I hope to see my team play this way next week," he said. "My players are good players, it was a good result."