Afghan police officers rescue a wounded German UN staffer, from a UN guest house during a gunbattle in Kabul, Afghanistan, Wednesday, Oct. 28, 2009. [Agencies]

KABUL: Gunmen with automatic weapons and suicide vests stormed a guest house used by UN staff in the heart of the Afghan capital early Wednesday, killing 12 people - including six UN staff - officials said. A Taliban spokesman claimed responsibility, saying it was meant as an assault on the upcoming presidential election.

Later, a rocket slammed into the grounds of the luxury Serena Hotel, which is favored by many foreigners. The device failed to explode but filled the lobby with smoke, forcing guests and employees to flee to the basement, according to an Afghan witness who asked that his name not be used for security reasons.

UN spokesman Adrian Edwards said six UN staff were killed and nine other UN employees were injured in the assault, which began about dawn in the Shar-e-Naw area of the city. Guests scurried from the building during the assault, and flames were seen on the roof as smoke billowed out and over the city.

Edwards said officials were trying to account for several other UN workers who were staying at the guest house. He did not know their nationalities but said they were non-Afghans.

"This has clearly been a very serious incident for us," Edwards said. "We've not had an incident like this in the past."

A security guard, Noor Allah, said he saw a woman screaming for help in English from a second story window and watched as terrified guests leapt from windows. Afghan police using ladders rescued at least one wounded foreigner.

Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack on the guest house and the Serena in a telephone call to The Associated Press, saying three militants with suicide vests, grenades and machine guns carried out the assault.

He said three days ago the Taliban issued a statement threatening anyone working on the Nov. 7 runoff election between President Hamid Karzai and Abdullah Abdullah.

"This is our first attack," he said.

Afghans vote Nov. 7 in a second round election after UN-backed auditors threw out nearly a third of Karzai's votes from the Aug. 20 ballot, determining widespread fraud. That pushed Karzai's totals below the 50 percent threshold needed for a first round victory in the 36-candidate field.

The Taliban warned Afghans to stay away from the polls or risk attacks. Dozens of people were killed in Taliban attacks during the August balloting, helping drive down turnout.

Mir Ahmed Formoly, 64, who lives near the guest house, said he heard the commotion and went outside where he saw muzzle flashes in the early morning light.

"I was so scared," he said. I went back inside the house."

He said gunfire and explosions lasted about two hours, punctuated by shouts and screams.

Mohammad Ayub, a shopkeeper who lives a few doors down from the attacked house, said he heard gunfire shortly before dawn. He assumed at first that it was an attack on a house belonging to relatives of President Karzai nearby, then saw that it was a different building.

"It was early morning, but I didn't have a watch on to know when. It was dark. Shooting started around this private guest house. I heard some shouts coming from inside the house," Ayub said.

"I heard boom! boom! several times. The fighting went on inside for about 10 or 15 minutes before the police came," he said.

The guesthouse attack was the third major one in the capital in recent weeks.

On Oct. 8, a suicide car bomber detonated his vehicle outside the Indian Embassy, killing 17 people - mostly civilians - and wounding at least 76 more. The Afghan Foreign Ministry hinted at Pakistani involvement - a charge Pakistan denied.

On Sept. 17, a suicide car bomber killed six Italian soldiers and 10 Afghan civilians on one of Kabul's main roadways.