Suicide bombers hit Afghan southeast

One bomber targeted the department for counter-narcotics, the officer said. The second detonated explosives inside the main intelligence headquarters a few hundred metres away, Guldad said.

"The bomber had managed to get inside the intelligence department by wearing the agency's uniform," he said.

Two intelligence officers and two police officers were killed and at least nine others wounded in the attack among officials in the intelligence department.

Gunfire also erupted inside the building, an official source said. It was not clear whether foreign troops were hit in either of the attacks.

Afghan and foreign troops had cordoned off the area and at least one helicopter belonging to foreign troops was hovering overhead, residents said.

Taliban insurgents claimed responsibility for the strikes, saying that three members of the Islamists group were involved and their target was the head of intelligence in Khost and his deputy, a Taliban spokesman said via a website.

A surge of violence in Afghanistan this year has marked the bloodiest period since the Taliban's removal in 2001. The violence has raised fears about Afghanistan's stability despite an increase in the number of foreign troops.

Regrouping in 2005, the al Qaeda-backed Taliban have carried out a number of high-profile attacks this year, including several in the capital, Kabul.

These included an assassination plot against President Hamid Karzai during a military parade near his palace. Officials say some members of the security forces helped the insurgents in that incident and in several other major attacks.

Separately on Thursday, authorities began a search of two prison cells where Taliban prisoners are held in the key Pul-i-Charkhi jail on the eastern outskirts of Kabul, the deputy justice minister said.

The aim of the search was to disarm prisoners possibly holding guns or knives, Mohammad Qasim Hashimzai told Reuters.

The prison has been the scene of a series of bloody riots in recent years. Thursday's search was the second this year.

In a major attack several months ago, Taliban fighters freed several hundred of their jailed comrades along with many other prisoners in the southern province of Kandahar.

A prisoner from the jail in Kabul telephoned Reuters to say that Afghan forces had opened fire during the operation and that there were some casualties among the inmates.

The sound of gunfire could be heard in the background. Hashimzai said he was not aware force had been used or if casualties had been reported.

(Writing by Sayed Salahuddin and Golnar Motevalli; Editing by Paul Tait)