KABUL — A powerful explosion near one of Kabul's few upscale hotels rocked the 140-room building late Saturday, knocking some guests from their restaurant chairs and shattering windows across the lobby and in many bedrooms.

No injuries were reported and no group immediately claimed responsibility for the blast near the Intercontinental Hotel, which sits atop a hill at the centre of the city. However, there were conflicting reports as to whether the explosion, which dug a crater in a garden about 50 metres behind the hotel, was caused by a rocket or a bomb.

One spokesman for the International Security Assistance Force, or ISAF, said a rocket smashed through a stone wall into the garden. "A rocket crater has been identified,'' said Squadron Leader Paul Rice.

But German soldiers at the site, members of ISAF whose sector includes the hotel, told The Canadian Press that the blast was caused by a bomb.

No Canadians were staying at the Intercontinental Hotel, which is often used by foreign business people and journalists. About 2,000 Canadian troops are stationed just outside Kabul as part of ISAF, but no Canadian soldiers were in the area around the Intercontinental at the time of the blast.

Police and soldiers from the 5,000-strong NATO-led security force rushed to the hotel after the blast and guarded its front door, as some guests quickly checked out in fear of another attack.

The explosion raised concerns about security in Kabul, where a loya jirga, or grand council, is scheduled for next month to ratify a new constitution. Some 500 delegates are expected to take part in the meeting, which is to be held near the Intercontinental and is considered a key step in Afghanistan's recovery from a quarter-century of war.

Taliban insurgents have launched an increasingly bold campaign throughout the country in recent months, often targeting relief agencies and coalition forces in southern and eastern Afghanistan. But attacks in the capital are relatively rare.

Saturday's attack came six days after a French refugee worker, Bettina Goislard, was gunned down south of Kabul, becoming the first international UN worker killed in Afghanistan since the fall of the Taliban.

Intercontinental director Arif Marcheen said the hotel was nearly full, and he had no idea who would have attacked it.

"Suddenly the lights went out, the explosion hit and the building shook,'' Marcheen said. "All the glass in the lobby shattered, but no one has been injured.''

He said a 30-metre wall of glass windows and doors rained into the lobby, while another hotel official, Albert Bester, said 60 per cent of the windows on the side of the hotel nearest the blast had been blown out.

Mike Breckon, an official of the Asian Development Bank who was staying at the hotel, said he had just sat down to dinner with colleagues when the explosion occurred.

"The curtains stopped the flying glass from injuring us,'' he said. "The room filled with smoke and some of the lights went out.''

Warren Young, a security officer from ADB also staying at the hotel, said some guests were knocked from their chairs at the restaurant.

He said he feared the attack is a sign Kabul is no longer an island of relative stability.

"We believe that we can now expect Kabul to become dangerous,'' said Young. "The loya jirga, which will be held nearby, will make this the biggest show in Afghanistan.''

However, Rice said ISAF had no plans to boost security in the capital. "We are already at a very high level of security,'' he said. "I don't think upping the security status would gain us anything.''

Two Canadian soldiers were killed in a landmine explosion on the outskirts of Kabul in October, but it was unclear if they were victims of a deliberate attack. Afghanistan is littered with mines after more than two decades of conflict.

In June, four German soldiers were killed and 29 wounded in a suicide attack on their bus. There also was an explosion between two abandoned buildings near the Intercontinental Hotel in August 2002, but peacekeepers said the blast didn't appear designed to cause serious damage or injuries.