DAMASCUS - The Islamic State (IS) militants have rigged the millennia-old city of Palmyra in central Syria with explosives, a monitor group reported on Sunday.

The IS militants planted mines and explosive devices in the ancient part of Palmyra, where 2,000-year-old monuments and temples are located, according to the Syrian Observatory for Human Rights.

It was not immediately clear whether the IS planted explosives to prevent the government troops from approaching, or to detonate the archeological sites as they previously did in Iraq, according to the London-based group, which relies on a network of activists on ground.

Last month, the IS detonated the notorious military prison in Palmyra, just days after capturing that city in the eastern countryside of the central province of Homs.

Palmyra, a UNESCO World Heritage site, contains monumental ruins of a city that was one of the most important cultural centers in ancient times. (Xinhua)