Islamic State (IS) militants in Syria have seized the ancient city of Palmyra and have entered the site containing prized ruins, reports say, the BBC reports.

The Syrian Observatory monitoring group says there are no reports yet of any destruction of artefacts.

It says IS also controls the nearby air base, prison and intelligence HQ. Syria has admitted it has pulled pro-government troops out of the city.

IS has previously demolished ancient sites in Iraq that pre-date Islam.