Hundreds of Osama bin Laden supporters clashed with English Defence League extremists today as a "funeral service" for the assassinated terror leader sparked fury outside London's US Embassy.
Police stepped in to separate the chanting groups amid threats of violence from both sides.
US leaders were branded "murderers" by radicals, who warned vengeance attacks were "guaranteed".
"It is only a matter of time before another atrocity - the West is the enemy," Abu Muaz, 28, from east London, said.
EDL members chanted "USA, USA" as Muslims knelt to pray for bin Laden at the opposite end of the highly-secured embassy, in central London.
An ambulance was called to the scene amid reports that one of the extremists had been attacked.
The pro-bin Laden event was organised by controversial preacher Anjem Choudary.
The former UK leader of the outlawed al-Muhajiroun and member of the "poppy-burning" Muslims Against Crusades extremist group called on the US to return bin Laden's body to relatives.
He has already warned of another 7/7-style terror attack in the wake of bin Laden's death.
Britain has followed the US in placing its embassies, diplomatic missions and military bases around the world on heightened alert in recent days.
The US said the decision to drop bin Laden's body into the North Arabian Sea was taken to avoid creating a shrine for the dead al-Qa'ida chief.
An EDL member slipped through police lines to unveil an effigy of bin Laden in the middle of the 300-strong group of extremist Muslims.
It prompted screams of "USA, burn in hell" and "Obama, burn in hell" from angry protesters.
Onlookers enjoying a sunny afternoon in Grosvenor Square were unimpressed.
Mary Smythe, 38, from Croydon, south London, said: "I think both sides are pathetic, quite frankly.
"It's disappointing and horrible to listen to the threats. They are all an embarrassment to this country."