Article published on the 2008-07-09 Latest update 2008-07-10 10:31 TU
Three assailants jumped from a car and shot at the police checkpoint, a witness told NTV television. The police returned fire, killing all three. Witnesses said that the whole attack lasted eight minutes.
A fourth assailant, driving the car, left the scene, and is now the target of a major police hunt.
Provincial governor Muammer Guler said that prosecutors specialising in terrorism cases have launched an investigation into the incident. He added that guns and rifles were seized at the scene.
No group has claimed responsibility.
"There is a host of groups that do have grievances against the United States. You have al-Qaeda... while at the same time you have far-left groups, maoist groups, that are still operating in Turkey which have been fighting the Turkish state for decades and who also have a very anti-American agenda," said correspondent Dorian Jones, speaking from Istambul.
"There are Kurdish groups too, although they are considered unlikely," he added.
No consulate personnel were injured, according to a US embassy spokesperson.
In 2003 Al-Qaeda members detonated a bomb outside the British consulate in Istanbul, at the same time attacking the British bank, HSBC.