Turkish police say a bomb explosion outside the office of a pro-Islamic magazine in Istanbul has killed one person and injured three others.

Police said Thursday that the device was placed outside the door of the monthly Adimlar magazine, on the third floor of a building, and exploded late Wednesday when the door was opened. Police identified the victim as 45-year-old Unsal Zor, who wrote for Adimlar, a magazine that is close to a Turkish militant Islamic organization.

There was no immediate claim of responsibility and the motive for the attack was not known. Police were investigating.

Video from the scene showed that the exterior wall of the office in the low-income Kagithane district had been ripped out from force of the blast.