In Afghanistan, a pre-dawn explosion at a guesthouse where United Nations staff were staying has rattled Kabul. International peacekeepers are investigating the cause. The blast occurred in the center of Kabul, down the street from a base housing the international peacekeeping force.

Lieutenant Colonel Jorg Langer from Germany is a spokesman for the peacekeeping contingent. "It was an explosion in a residential area, and only a wall was damaged, and windows were burst."

Residents at the guesthouse included staff members of the U.N. Assistance Mission in Afghanistan, which has been targeted in recent attacks outside the capital. Police say the explosion was probably an accident involving a gas cooker, although news reports quote at least one police official as saying it was a bomb. Lieutenant Colonel Langer says investigators with the peacekeeping force are looking into the explosion.

The incident comes as Afghanistan's constitutional assembly is meeting in Kabul to decide on the country's future system of government. Anti-government insurgents have threatened to attack the assembly, and two earlier series of explosions, both attributed to rockets fired from outside the city limits, have occurred since the gathering began on December 14. No casualties have been reported in any of the incidents.

Lieutenant Colonel Langer says Kabul remains relatively peaceful, but adds that peacekeepers and police are on guard against any attacks. "The security situation, despite this explosion, [is] calm, we can say, but not stable."

The peacekeepers and Kabul police are maintaining tight security in the capital, barring all public traffic near the constitutional assembly site and maintaining checkpoints throughout the city.