Taliban attacks are intensifying as the U.S.-led coalition prepares to withdraw most of its soldiers by the end of 2014.

At least two people were killed in the second attack in three days on expatriate aid workers' housing, and authorities fear hostages may have been taken inside the compound in Kabul's western Karte Seh district.

Gunfire and explosions could be heard late into the evening and police said the building's second floor had caught fire.

At least two insurgents with suicide vests were also killed, one by his own explosives and the other was shot, Qadam Shah Shaheem, commander of the Afghan army's 111 Military Corps Kabul, said.

He said eight people, including two foreigners, were rescued from the building but it was unclear how many attackers were still on upper floors.

"We are afraid the attackers may have taken some people hostage. We are therefore acting very cautiously to avoid casualties," Shaheem said.

He said two bodies were found on the lower floors, but their identities were not known. He did not know the name of the aid organization.

The Taliban insurgents claimed responsibility, with a spokesman saying in a statement that their fighters had targeted a Christian organization seeking to convert Muslims.

On Thursday, Taliban gunmen had stormed a guest house in Kabul's diplomatic quarter. Only the attackers were killed.

In southern Afghanistan, soldiers were still fighting Taliban gunmen inside Camp Bastion, a major southern base handed over to Afghans by the British and U.S. militaries in October.

A few dozen Taliban fighters with automatic weapons and suicide vests had attacked the base in Helmand province on Thursday, General Ayatullah Khan, commander of the army regiment in the area, said.

"Some managed to get inside, took position, and started the gunfight," he said, noting that the insurgents appeared to be holed up in one of the smaller camps within Camp Bastion.

At least five soldiers and 26 insurgents were killed on Friday at the base, Omar Zwak, a spokesman for Helmand's governor, said.

The Taliban, who were ousted from power by the U.S.-led coalition in 2001, claimed that hundreds had been killed in the attack. The insurgents routinely inflate casualty figures.