Turkish police on Sunday killed in a clash two suspected ISIS members believed to have been planning an attack in the capital Ankara, the regional governor said.

The two, in their 20s, were killed during a police operation on their residence in the Etimesgut district after a gunfight with officers, state-run news agency Anadolu quoted governor Ercan Topaca as saying.

It said the two men killed were believed to be planning an attack and police seized weapons and explosives in the apartment in the operation launched after a tip-off from a suspect detained in Istanbul.

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.

The raid occurred ahead of the ruling AK Party’s congress in the city on Sunday, when it was expected to elect President Recep Tayyip Erdogan as leader after constitutional reforms approved last month in a referendum granting him sweeping new powers.

ISIS jihadists 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 Istanbul’s Reina nightclub that killed 39.

NATO member Turkey is part of the US-led coalition against ISIS and launched an incursion into Syria last August to drive the jihadist group and Kurdish militia fighters away from its borders.