Isis Palmyra destruction
Isis is pressing on with its 'cultural cleansing' of the historic Syrian city of Palmyra Gustau Nacarino/Reuters

Russian warplanes have targeted Islamic State (Isis) in the Syrian ancient city of Palmyra, according to Syrian state television.

The aerial bombings destroyed 20 vehicles and three weapons depots in the city, according to the report. Raids also took place in Aleppo, targeting the towns of al-Bab and Deir Hafer, 20km east of a military airport currently under siege by IS.

The air strikes come after officials and local sources said IS blew up another monument in the 2,000-year-old Unesco world heritage site. The Arc of Triumph was "pulverised" by the militants, who seized the city in May, according to an activist from Palmyra. The UK-based Syrian Observatory for Human Rights (SOHR) confirmed the report, citing sources on the ground.

The group already destroyed two ancient temples at the city, described by the UN as a site of "outstanding value". Syrian antiquities director Maamoun Abdulkarim told Reuters that if IS remains in control of Palmyra, "the city is doomed".

"They want to raze it completely," he told AFP.