The Ukraine forward came off the bench and drilled home from Michail Antonio's assist on 89 minutes as the Hammers sunk the Blues at the London Stadium.

Tomas Soucek was denied a first-half goal by the Video Assistant Referee, but the Czech midfielder later did force a goal that stood.

Willian put Chelsea ahead from the penalty spot before Soucek levelled in first-half added time.

Antonio fired the Hammers in front six minutes after the break but Brazil forward Willian whipped home a fine free-kick to level for Chelsea in the 72nd

Yet as the Blues pressed for a winner, West Ham broke at pace and Yarmolenko sealed a big win in the Hammers' fight for survival - and also a league double over their London rivals.

West Ham pulled themselves three points clear of the relegation zone, while Chelsea missed the chance to leapfrog Leicester into third place.

Chelsea boss Frank Lampard criticised his players for the latest in a string of below-par losses that have followed patches of fine form this term.

"We had an opportunity to move third. If there's moments when you switch off you are going to encourage teams on," Lampard told Sky Sports.

"Listen, we're two points ahead of Manchester United, who have been playing fantastically and are on a great run. Wolves are having a great season and they are two points behind us.

"So there's perspective, but we're upset because we want to win the game ... I can't help but tell the truth, it's a game we should win tonight."

Pierre-Emerick Aubameyang fired a brace as Arsenal overwhelmed Norwich 4-0 at the Emirates Stadium.

The striker took his Premier League tally to 19 goals for the campaign, with Granit Xhaka also on target for the Gunners.

Cedric Soares lashed in a late goal on his debut for Arsenal, with the ex-Southampton defender finally fit after a string of injury issues having joined the club in January.

Richarlison's 13th goal of the season in all competitions and a Gylfi Sigurdsson penalty proved enough for Everton to see off Leicester 2-1 at Goodison Park.

Kelechi Iheanacho hit back for the Foxes, but Brendan Rodgers' men slipped to a fourth match without a win in all competitions and sit just three points ahead of top-four chasing Manchester United and Wolves.

Allan Saint-Maximin laid on a hat-trick of assists as Newcastle thumped relegation-threatened Bournemouth 4-1 on the south coast.

Dwight Gayle, Sean Longstaff, Miguel Almiron and Valentino Lazaro found the net for Steve Bruce's Magpies, who hit back in style after their 2-0 FA Cup quarter-final defeat by Manchester City.

Dan Gosling claimed a late goal for Bournemouth against his former side.

Eddie Howe's men slipped below Aston Villa on goal difference to 19th in the table.

Australian Associated Press