Istanbul, 10 July (AKI) - While no group has claimed responsibility for the attack on the US consulate in Istanbul, there is growing speculation that al-Qaeda was behind the shootings.

Turkish security sources told local media that all three assailants were from eastern Turkey and were suspected of being members of a group linked to al-Qaeda.

Three policemen and three gunmen died in a gun battle outside the US consulate in the Turkish city of Istanbul on Wednesday.

Funerals were being held for the three police officers on Thursday.

Two men have been detained over alleged links to the attack and police are searching for another man who fled from the scene.

One of the men detained is reportedly the brother of one of the attackers.

While no staff were injured inside the consulate, the US ambassador to Turkey condemned the attack as an "act of terrorism" and US State Department spokesman Sean McCormack said he could not rule out suspicions that al-Qaeda was behind the attack.

"At this point one can't rule that out, but I also can't support at this point, those suspicions," McCormack said. "We're continuing our efforts to work with the Turkish government to determine who is responsible for it."

According to the Hurriyet newspaper, Wednesday's attack may have been to avenge the death of an al-Qaeda militant reportedly killed in Afghanistan by a US bombing.

The al-Qaeda militant and two of the three dead consulate assailants are from the same southeastern province in Turkey.

An official told Hurriyet that the three gunmen who were killed in the attack had only recently returned to Turkey after a period of time in Afghanistan. This has led to speculation that they may have received training at an al-Qaeda camp.

The official also added that the assailants were members of a Turkish Sunni Islamic fundamentalist group, known as the Great Eastern Islamic Raiders Front, or IBDA-C.

Istanbul police raided a number of addresses across the city and reportedly seized documents related to al- Qaeda.

As yet no clear motive for the attack has been identified and it is still unclear whether the attackers were trying to force entry into the consulate compound or, as some media reports have claimed, simply to attack Turkish police guarding the compound.

In 2003, al Qaeda claimed responsibility for devastating bombings of the British Consulate in Istanbul, the local headquarters of the HSBC Bank and two synagogues.

Fifty-eight people died in those attacks, including British Consul-General Roger Short.