ISTANBUL, Turkey, (AP) – A Turkish government official says there are signs that the gunmen who attacked the U.S. consulate in Istanbul might have been inspired by al-Qaeda but there is no firm evidence yet.

The official, who is close to the investigation, says the ties of the three attackers who were killed by police outside the consulate were being probed. Three police were also killed.

The official spoke on condition of anonymity Thursday because he is not authorized to speak to the media.

The Hurriyet newspaper suggests that Wednesday’s attack could have been to avenge the death of an al-Qaeda militant reportedly killed in Afghanistan by a U.S. bombing. The al-Qaeda militant and two of the three dead consulate assailants are from the same southeastern province in Turkey.