A Kurdish official in the northern Iraqi city of Irbil says a suicide car bomber has struck in the heart of the city, inflicting an unknown number of casualties.

Wednesday's bombing in Irbil, capital of the semi-autonomous Kurdish region in northern Iraq, took place near the historic citadel.

Mayor Nawzad Hadi told the state-run Rudaw TV channel that the number of casualties was not immediately known.

Hadi says the suicide bomber tried to enter the citadel but failed, so he detonated his car outside the gates. The mayor says there is significant damage to the property in the area.

Irbil is close to the front-lines. Islamic State militants advanced within 30 kilometers of the Irbil last summer, but were eventually repelled by Kurdish forces with the help of U.S. airstrikes.