Baghdad (IANS) -- The Islamic State (IS) terrorist group damaged an ancient citadel and destroyed two shrines in Iraq's northern province of Nineveh, an official from the provincial government said Wednesday. The militants planted bombs in the northern and western parts of the ancient Tal Afar citadel, which is located in the militant-seized town of Tal Afar, some 70 km west of provincial capital Mosul, and blew them up before noon, destroying large parts of the ancient walls of the fortress, Mohammed Ibrahim al-Baiyati, head of the provincial security committee, told Xinhua. The militants apparently are continuing to blew up the remaining parts of the ancient citadel walls, Baiyati said, adding that the militants reportedly excavated some of the ruin sites in the citadel looking for some antiquities, probably to sell them to fund their activities. The Tal Afar fortress is believed to be a remnant from the Assyrian period. After the US-led invasion in 2003, the site inside the citadel has been used as the house of the city's mayoral, municipal and police headquarters before the IS militants seized the town in June. Baiyati also said the IS militants Tuesday blew up the shrines of Imam Muhsin and Sultan Waiys in the city of Mosul, some 400 km north of Iraq's capital Baghdad, Baiyati said. The extremists are believed to have damaged or destroyed 30 shrines and 15 Shia and Sunni mosques in July, including the shrine of Nabi Shiet (Prophet Seth) and the shrine of Nabi Younis (Prophet Jonah) in the city of Mosul. The two shrines are revered in Islam as well as in Christianity and Judaism.