Istanbul (AP): Armed men attacked a police guardpost outside the U.S. consulate in Istanbul on Wednesday, an assault that Istanbul's governor said killed three attackers and three policemen.

A U.S. Embassy spokeswoman said there were no reports of casualties among American consulate employees, but could not confirm Turkish media reports of injuries and deaths.

``Three policemen were martyred and three attackers were killed,'' Gov. Muammer Guler told reporters at the scene, adding that authorities were pressing to identify the attackers and any group to which they belonged.

``At about 11 a.m., at least one assailant opened fire on the Turkish police guardpost area near the main entrance to the consulate,'' the U.S. embassy spokeswoman said, speaking anonymously due to the sensitivity of the matter.

``We're cooperating with the police and taking the appropriate measures,'' she said.

The attack occurred right outside the high-walled consulate compound in Istinye district.

Yavuz Erkut Yuksel, a bystander, told CNN-Turk television the attackers emerged from a white vehicle and surprised the guard.

``One of them approached a policeman while hiding his gun and shot him in the head,'' Yuksel said.

Guler said two people, including a policeman and the driver of a towing vehicle, were also injured.

Television footage showed four people lying on the ground at the foot of the consulate's wall. Medics were seen trying to help one of them.

There was no immediate comment from police or authorities.

The secure U.S. consulate building was built after homegrown Islamic militants linked to al-Qaida carried out suicide bombings in 2003 that targeted two synagogues, the British Consulate and a British bank in Istanbul, killing 58 people.