The UK-based Syrian Observatory for Human Rights says ISIL militants have captured most of Palmyra in eastern Syria, following a surprise assault.

The group says there are fears for the lives and safety of civilians inside the city because many of them are pro-government supporters. A news agency affiliated with the extremist group also released a video on Saturday, showing ISIL fighters advancing south of the ancient city.

The Syrian Army says they have sent troops to fight the militants. Many residents were killed and a lot of historical relics were damaged when ISIL broke into the city last May. However, Syrian government troops recaptured Palmyra in March. The two-thousand-year-old city has been listed by UNESCO as a World Cultural Heritage Site.