Islamic State militants have taken full control of the ancient city of Palmyra in central Syria, a monitor group reported on Thursday.

Both the residential and the historic areas of Palmyra, which host 2,000-year-old monuments and temples, have fallen to the IS group, according to the London-based Syrian Observatory for Human Rights.

An air base, a central prison and the intelligence headquarters are all in IS hands now, said the monitor group, which says it relies on a network of activists on the ground inside Syria.