Updated at 6:07 p.m. ET
KABUL, Afghanistan In the latest militant strike on the Afghan capital, Taliban gunmen backed by a suicide car bomber attacked an international aid group's compound on Friday, killing two guards and setting off an hours-long street battle with police in the heart of Kabul .
The attack, the second in the city in just over a week, also left four International Organization for Migration workers wounded including an Italian woman badly burned by a grenade. Thirteen police were wounded while all six attackers died in the assault, authorities said.
Taliban spokesman Zabihullah Mujahid quickly claimed responsibility for the attack, telling CBS News' Mukhtar Ahmad the building targeted was being used by U.S. agents. His claims could not be verified, and the Taliban often exaggerate their successes in similar attacks.
At the chaotic scene of the siege, dozens of Afghan police took cover behind blast walls and rushed around through a thick cloud of smoke made by the bomb. At least one wounded officer was seen being helped away by his comrades.
The insurgents have unleashed a wave of bombings and assassinations around the country, testing Afghan security forces' ability to respond with reduced help from international forces, who have begun a withdrawal that will see most foreign troops gone by the end of 2014.
A Nepalese guard and an Afghan police officer providing security to the compound died in the assault as well as all of the attackers, said Kabul police chief Mohammad Ayoub Salangi.
The attackers stormed into the building with grenade launchers after blasting open the compound's gate with the car bomb, Salangi said. He said police were able to evacuate the guest house with none of the residents killed.
From when the initial blast shook much of the city in the late afternoon until well past nightfall, fighting was still going on in the upscale Shahr-i-Now neighborhood, home to several international groups' fortified compounds as well as the headquarters of the Afghan Public Protection Force and a hospital run by the National Directorate for Security.
Security forces were able to enter the building in late evening and by 10:30 p.m. the siege was over, according to Sediq Sediqi , spokesman for the Afghan Ministry of Interior.
"Fortunately, it is finished. The last attacker has been killed by the police," Sediqi told The Associated Press. Local television reporters demanded to know how a car bomber and five attackers could enter the capital, but Sediqi portrayed the battle as a victory for security forces.
"We were successful because we prevented civilian casualties," he said. He said adding that 13 police were wounded in the fighting.
"Wild terrorists attacked ... the IOM," police official Zemarai Bashari told The Associated Press at the scene. "Our forces are fighting the enemy with courage and honesty."
IOM spokesman Chris Lom told the AP in Geneva that an Italian woman working for the group was seriously burned by a grenade thrown into the compound by the attackers.
Taliban spokesman Zabiullah Mujahid said insurgent fighters killed several people in the compound, which he said was targeted because it is "the place of residence of trainers for the CIA." He said late in the afternoon that he was in contact with the attackers and that their "morale is high" despite the fierce fighting.
Initial reports identified the target as a United Nations compound. However, the U.N. special representative to Afghanistan, Jan Kubis, said in a statement that all U.N. staff in Kabul were accounted for.
The IOM is an inter-governmental organization based in Geneva that helps resettle people worldwide. It operates in Afghanistan in a mission coordinated by the U.N. but is not an agency of the world body.
Last Thursday in Kabul,, and nine Afghan bystanders in an attack on a U.S. convoy. Another insurgent faction, Hizb-i-Islami, claimed that bombing.
Militants have staged dramatic assaults in the past on Afghan security and international targets in the capital, but the two months before that had been relatively calm there.
As the Taliban spring offensive gets underway, however, it will test the Afghan forces' ability to keep security now that international combat forces are pulling back ahead of the 2014 withdrawal.
Most of the U.S.-led military coalition will leave by the end of next year, more than a dozen years after launching the war to topple the Taliban regime over its sheltering of al Qaeda's leadership.
The coalition on Friday condemned the attack and praised the work of the Afghan forces, saying that international personnel provided only medical support.
"Their prompt and effective action saved the lives of other innocent Afghans and members of the international community," said Gen. Joseph F. Dunford, the commander of international forces.
International forces have trained some 350,000 Afghan soldiers, police and other security units under the plan to turn over full responsibility for fighting the Taliban and other militants when most foreign troops leave.