LONDON: West Ham United on Wednesday vowed to ban for life any fans found to have taken part in an attack on the Manchester United team bus before their key Premier League game.

The attacked marred West Ham's 3-2 win over the English giants in the final match at the London club's Boleyn Ground on Tuesday.

The match was delayed for 45 minutes as police in riot gear cleared troublemakers who hurled bottles and cans at the bus while United's players cowered on the floor.

“It was an extraordinary night full of extraordinary moments in front of extraordinary fans, 99 percent of whom behaved impeccably and were a credit to the club,” West Ham said in a statement.

“However, we are aware that there were some supporters outside the Boleyn Ground who didn't act in an appropriate way when the Manchester United team bus was damaged.

“That was not acceptable and we will work with the police to identify those responsible and ban them for life.”

London police said four officers were injured during the trouble, but no arrests have yet been made.Three men were arrested during the game, including a 20-year-old on suspicion of affray and two men aged 47 and 18 for rushing onto the pitch.

Police are scouring closed circuit television images of the incidents and have appealed for witnesses.West Ham co-chairman David Sullivan initially blamed United for the delay to kick-off, saying they should have arrived earlier at the ground, but on Wednesday he backtracked.

“When I was asked about the incident prior to yesterday's game, I was unaware of the damage that had occurred to the Manchester United team bus,” he said in a statement on the West Ham website.

“I want to apologise to Manchester United for that damage and assure them that we will be doing all we can to track down those responsible and ban them for life.”

West Ham vice-chairman Karren Brady condemned the bus attack.

“I, the board and everyone at West Ham United totally condemn the unacceptable behaviour we saw outside the ground last night,” Brady wrote on Twitter.

“West Ham is a family club and the vast majority of fans attended Tuesday's final game to respectfully say Farewell Boleyn.

“Those who chose to behave unacceptably will be dealt with in the strongest way possible, with life bans for those guilty of violence.

“The events in the stadium last night were incredible and it would be a shame if the actions of a mindless few outside overshadowed them.

“Their behaviour was unacceptable and won't be stood for. But my overriding memory will not be of them but of a fitting farewell to the Boleyn.”