Islamic State group fighters advanced to the gates of ancient Palmyra Thursday, raising fears the Syrian world heritage site could face destruction of the kind the jihadists have already wreaked in Iraq. IS fighters were battling Syrian troops less than two kilometres (barely a mile) from the remains of one of the most important cultural centres of the ancient world, Syria's director of antiquities said. The jihadists reached the oasis town after a lightning advance across the desert in which they overran government forces in fierce fighting that cost the lives of 110 combatants, the Syrian Observatory for Human Rights said. "Palmyra is under threat," said Observatory director Rami Abdel Rahman.