Furious Afghans torched an effigy of US President Barack Obama and hurled stones at police Sunday during a mass protest over allegations that Western troops set fire to a copy of the Koran.

A crowd of around 1,000 demonstrators, mainly university students, marched through the streets of the capital Kabul before massing in front of the national parliament building and hurling stones at riot police as well as an armoured vehicle which blocked them from going down one street.

Police responded by firing into the air, dispersing the crowd for a brief period before they massed again.

The demonstrators, almost all men, chanted: "Death to America, death to Jews and Christians!" as they burned a model of Obama and a United States flag. Some wore black ribbons on their foreheads, calling for a jihad.

"We have gathered here to express our disgust towards the American troops and their act of burning and insulting our holy book of Koran," Ihsanullah Hakimi, one of the demonstrators, told AFP.

At one stage, the deputy speaker of parliament came out to address the crowds, saying they had the support of parliament.

"It is not the first time that they have shown their disgust for the Koran. We are with you and it is a good democratic way you demonstrate," said Mohammad Saleh Saljoki.

The protest follows widely-circulated rumours that international troops -- part of a 100,000-strong Western military deployment in Afghanistan -- burned a copy of the Muslim holy book during an operation against Taliban rebels in the province of Wardak, south of Kabul, earlier this month.

The claims have been rigorously denied by NATO and Afghan authorities who say they are being falsely circulated to whip up hatred against the West.

Habibullah, one of the organisers of the demonstration, claimed that events in Wardak were part of a pattern of abuse of the Koran.

"This kind of incident takes place across the country," he said.

There had been similar demonstrations but on a smaller scale in the eastern city of Jalalabad and southern Kandahar earlier last week.

A spokeswoman for the NATO-led International Security Assistance Force (ISAF) said that the claims had been investigated and found to be groundless.

"The investigation determined that neither ISAF nor the Afghan national army had burned any Koran in Wardak province," the ISAF spokeswoman told AFP.

Shahedullah Shahed, a spokesman for the Wardak government, also dismissed the allegation, saying the "false report" of Koran being insulted could be spread by Taliban insurgents to stir up resentment towards Western troops.

"It was some 11 days ago. When the news came to us we dispatched a delegation to investigate," said Shahed.

"While our investigation showed that a copy of Koran was burnt, it was not foreign soldiers, but rather the work of some drug addicts, maybe paid by Taliban to spark resentment towards us and the foreign forces."

Afghanistan is a deeply conservative country and accusations of religious abuse have previously proved inflammatory.

A Lithuanian soldier and two Afghans were killed in May last year as demonstrators tried to storm a military base in the remote western province of Ghor in the wake of allegations of abuse of the Koran by US troops in Iraq.

Meanwhile in a bid to head off another backlash by civilians, ISAF announced it had launched an investigation into the deaths of four civilians who were killed when troops fired on their vehicle in Kandahar on Saturday.

However it said an initial report had shown the forces opened fire when the driver ignored warnings to stop while approaching at speed.

Provincial authorities had earlier said two women and a child were among the dead, while two or three other civilians were also wounded.