Protests erupted outside the main US military base in Afghanistan and in Kabul on Tuesday over allegations that foreign troops had set fire to copies of the Koran, police said.

File photo of US soldiers on patrol outside Bagram airbase. Protests erupted outside the main US military base in Afghanistan and in Kabul on Tuesday over allegations that foreign troops had set fire to copies of the Koran, police said. (AFP Photo/Shah Marai)

Thousands of protesters besieged Bagram airbase, north of Kabul, throwing petrol bombs which set fire to a gate, an AFP photographer said.

The US commander in Afghanistan, General John Allen, said he had ordered an investigation into a report that troops at Bagram "improperly disposed of a large number of Islamic religious materials which included Korans".

"I offer my sincere apologies for any offence this may have caused, to the president of Afghanistan, the government of the Islamic Republic of Afghanistan, and most importantly, to the noble people of Afghanistan," he said.

A local police official said more than 2,000 people were demonstrating outside the sprawling US-run base.

"They are demonstrating over the burning of copies of the Koran inside the base," the official told AFP.

Sidiq Siddiqi, an interior ministry spokesman, confirmed the demonstration and said reinforcements were sent to the area, about 60 kilometres (40 miles) north of the capital to prevent possible violence.

Another protest by about 500 people broke out in the Pul-e-charkhi district of Kabul not far from major NATO bases on the Jalalabad road, police spokesman Ashamat Estanakzai told AFP.

"The police have the crowd in control, it is not violent," he said.

Similar protests have in the past turned violent in Afghanistan, an extremely devout Islamic nation where an insult to the religion carries the death penalty.

About 10 people were killed and dozens of others were injured during days of unrest unleashed last April over the burning of a Koran by American pastor Terry Jones in Florida.

Source: AFP