KABUL - Eleven Taliban suicide bombers attacked government buildings in eastern Afghanistan on Tuesday, sparking running gun battles that killed at least 20 people.

Doctors reported more than a dozen wounded in the fighting, but said at one point they were unable to reach many other casualties because of the danger.

The U.S. military said three American soldiers were wounded in the fighting, but that U.S. and Afghan troops were able to free 20 hostages taken by the insurgents.

The assault began around 10 a.m. when a suicide bomber in a burqa attacked the governor's compound in Khost, an eastern city on the border with Pakistan that houses a major American base. That blast was followed soon after by a suicide car bomb explosion, said Wazir Pacha, a spokesman for the provincial police chief.

U.S. forces attending a nearby meeting responded to the attacks and killed an unknown number of insurgents, said Lt.-Cmdr. Christine Sidenstricker, a U.S. military spokeswoman.

Khost residents hid from booming explosions and running street clashes that lasted until 5 p.m. At least eleven insurgents and nine others - including police and civilians - died, the Defence Ministry said.

A Taliban spokesman, Zabiullah Mujahid, claimed that 30 suicide bombers had attacked the government buildings.

The assault began with several suicide attacks on the Khost governor's compound, which drew small arms fire from nearby U.S. troops, a U.S. military spokesman said.

Then a team of six suicide bombers tried to attack the nearby police headquarters, but were rebuffed by security forces and entered the neighbouring municipal building, said Pacha, the Afghan police spokesman.

Three bombers detonated their explosives, the Interior Ministry said, while other militants took 20 city employees hostage, Pacha said.

After the insurgents entered the municipal building, a number of explosions reverberated inside as U.S. and Afghan forces surrounded the area, an Associated Press stringer said from within the police chief's compound.

U.S. and Afghan forces later stormed the building, freed 20 hostages and killed three insurgents, Pacha said.

A second U.S. team was sent from the nearby American base, Camp Salerno, but those troops were fired on en route.

A U.S. soldier and an Afghan policeman were wounded and taken to Camp Salerno for treatment where they were in stable condition, officials said. A number of rebels were reportedly killed in the clash.

The Taliban have carried out an increasing number of complex attacks in recent months and over the last three years they have gradually increased their control over wide swaths of territory.

Military analysts have said the increasing sophistication of attacks in Afghanistan is a result of training by Pakistani militants and al-Qaida fighters.

President Barack Obama hopes to reverse the rebel momentum and has implemented a new strategy for the region. As part of that plan, the Pentagon fired Gen. David McKiernan, the top U.S. commander in the country, on Monday and replaced him with Lt.-Gen. Stanley McChrystal, a former leader of special forces.

Obama has also appointed a former three-star general as the U.S. ambassador to Afghanistan. Karl Eikenberry presented his credentials to President Hamid Karzai on Tuesday.

Gen. Mohammad Zahir Azimi, Afghanistan's Defence Ministry spokesman, listed three priorities that McChrystal should focus on.

Prevent civilian casualties, strengthen the quality and quantity of Afghan forces, and focus more on co-ordinating the military operations with Afghan forces," Azimi said.

McKiernan's exit comes as more than 21,000 additional U.S. forces begin to arrive in Afghanistan - dispatched by Obama to confront the Taliban more forcefully. A record 38,000 U.S. troops are already in the country.