Turkish police killed two suspected Islamic State militants in a clash during a raid on an apartment in the capital Ankara overnight, state-run Anadolu news agency reported on Sunday.
It said the two men killed were believed to be planning an attack and police seized guns and grenades in the apartment in an operation launched after a tip-off from a suspect detained in Istanbul.
The raid occurred ahead of the ruling AK Party's congress in the city on Sunday, when it was expected to elect President Tayyip Erdogan as leader after constitutional reforms approved last month in a referendum granting him sweeping new powers.
Ankara's Governor Ercan Topaca told Anadolu at the scene of the raid that the detained suspect, an Azeri citizen, was still being questioned in Istanbul and was believed to have brought the two men to Ankara by car, Anadolu said.
Islamic State militants have been blamed for bomb and gun attacks in Turkey in the past, including an attack on Istanbul's main airport which killed more than 40 people last June and a New Year's Day shooting in an Istanbul nightclub that killed 39.
NATO member Turkey is part of the US-led coalition against Islamic State and launched an incursion into Syria last August to drive the jihadist group and Kurdish militia fighters away from its borders.