MOSUL, Iraq, June 20 (Reuters) - Militant Sunni Islamists who seized swathes of northern Iraq last week have destroyed symbols of Iraq's heritage in the city of Mosul, including statues of cultural icons and the tomb of a medieval philosopher.

Witnesses said militants from the Islamic State in Iraq and the Levant (ISIL) had destroyed a statue of Othman al-Mousuli, a 19th Century Iraqi musician and composer, and the statue of Abu Tammam, an Abbasid-era Arab poet.

The tomb of Ibn al-Athir, an Arab philosopher who traveled with the army of warrior sultan Salahuddin in the 12th century was desecrated after ISIL took the city. Witnesses said the domed shrine had been razed and a park around it dug up.

ISIL and other militants, whose strict Salafi interpretation of Islam deems the veneration of tombs to be idolatrous, have destroyed several tombs and mosques inside Syria and now in neighboring Iraq where they have seized towns and cities.

Militants also stole around 250 horses from the governor of Mosul's house and took control of cereal silos, the witnesses said. They said some of the horses that were too sick to be moved were killed.

State television, run by the Iraqi government which is fighting ISIL, said the militants had imposed a tax on Christians living in the city. Reuters could not independently confirm the report. Most of Mosul's Christians have fled the city. (Writing by Oliver Holmes; Editing by Robin Pomeroy)