Two explosives have been thrown at a US consulate in Adana, southern Turkey, damaging the building but injuring no one.
Only one of the devices exploded, causing some damage to a wall and shattering windows. Another was defused by the police.
A man who had been waiting in an immigration queue has been arrested and has - according to some reports - admitted to throwing the devices at the consulate.
The suspect, Cumali Kizilgoca, said the attack was in retaliation for an attempt by Israel to assassinate a Hamas leader in Gaza on Tuesday, Turkish television reported.
But Turkish officials in Ankara have said they do not know why he threw the explosives, suggesting he may be mentally unbalanced.
The government expressed regret at the incident - the first attack on US interests in Turkey since the war on Iraq, which many Turks opposed.
The suspect reportedly said that he had crossed the police barriers under the pretext of getting immigration papers and that when police questioned him, he hurled two hand grenades.
For security reasons, the United States is planning to transfer the consulate - which is currently in the centre of town - to a new building outside the city, Turkish television reported.