The White House on Wednesday issued a strong condemnation of the attack in which six people died near the US consulate in Istanbul.
"We strongly condemn the attack," said Tony Fratto, a White House spokesman.
Asked if the United States considered it a terrorist attack, and if its consulate was targeted, Fratto said "I'm not yet in a position to comment on the facts or nature of the attack."
In Ankara, however, US Ambassador to Turkey Ross Wilson called the assault by three gunmen on a guardpost outside the US consulate in Instanbul, "an obvious act of terrorism" aimed at the United States.
Three gunmen and three Turkish policemen were killed earlier Wednesday in the attack outside the well-fortified US consulate in Istanbul.
The assailants "directly" targeted the police post outside the high-walled US consulate in the upscale district of Istinye, Istanbul Governor Muammer Guler said.
They jumped from a car and opened fire at the post around 11:00 am (0800 GMT), a witness told NTV television, adding that they also fired shots at the building.
The security forces returned fire, killing all three gunmen.
One policeman died on the spot, while two others succumbed to their injuries in hospital, Guler said.
Two other people -- a policeman and the civilian driver of a police truck -- were injured, he said.
Wilson said no Americans were killed and praised the quick work of the police response.
"The persons who lost their lives are Turkish citizens and we are very sad about that," he said.
Security measures were beefed at the consulate as well as at the US embassy in Ankara and the consulate in the southern city of Adana, near which a major Turkish air base is often used by US aircraft, Wilson said.
