ISTANBUL, April 27 (Xinhua) -- Turkish police on Friday captured a suspected sub-leader of the Islamic State (IS) and three other militants in an operation in the western province of Izmir, local media reported.

The so-called sub-leader was a close friend of former IS leader Abu Bakr al-Baghdadi, the Hurriyet daily said, noting he was shown as the successor of al-Baghdadi.

There are conflicting reports, however, about the status of al-Baghdadi, with some saying he was wounded or killed in airstrikes while some say he is alive and in hiding.

According to Hurriyet, the IS sub-leader has been the commander of the city of Deir al-Zour in eastern Syria and was involved in the massacre of 700 people in the country on Dec. 14, 2017.

The suspects were caught by police among a group of Syrian refugees who had been waiting in the city of Izmir to illegally cross into Europe, the report said.

Turkey, hit by a series of deadly attacks by IS militants over the last two years, has been tightening operations against the group in recent months as it is suffering defeat in neighboring Iraq and Syria.