BEIRUT - Islamic State jihadist fighters took control of the northern sector of the Syrian city of Palmyra on Wednesday, a monitor and activists said, sparking renewed fears over its historic treasures.
"The situation is very bad," Syrian antiquities director Mamoun Abdulkarim said by telephone.
"If only five members of IS go into the ancient buildings, they'll destroy everything," he added, calling for international action to save the city.
Palmyra's UNESCO world heritage site ruins, including ancient temples and colonnaded streets, are in the city's southwest.
Hundreds of statues and ancient artefacts from Palmyra's museum have already been transferred out of the city, Abdulkarim said, but many others - including massive tombs - could not be moved.
It was the second time IS has overrun northern Palmyra, after it seized the same neighbourhoods on Saturday but held them for less than 24 hours.
Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, said IS fighters had seized roughly "a third of Palmyra" on Wednesday.
After fierce clashes on the northern edges of the city, IS entered the northern quarter "without their vehicles."
They seized a state security building and fanned out across northern districts as regime forces fled, the monitoring group's head said.
"People are very afraid of what will happen, because IS has the capability to get to the heart of Palmyra," said Khaled al-Homsi, an activist in the city. He said terrified residents were staying at home and that government forces were "on the defensive."
Asked if IS would be able to reach the city's ancient ruins, a Syrian military source said "everything is possible in urban warfare."
He acknowledged the jihadists had infiltrated northern neighbourhoods and said they were engaged in "street fighting" with regime forces.
Mohammad Hassan Homsi, another activist originally from Palmyra, told AFP that "regime soldiers fled after IS took the state security building".
"They headed to the military intelligence headquarters near the ruins," he said.
Homsi said jihadists from the flashpoint border town of Kobane, where US-led air strikes helped Kurdish fighters defeat IS in January, were among those fighting in Palmyra.
IS began its offensive on the ancient city on May 13, seizing a nearby town and two gas fields, and leaving more than 350 people dead.
Antiquities officials fear IS wants to destroy Palmyra's pre-Islamic cultural treasures, which include colonnaded streets and ancient citadels.
The city is also strategically located at the crossroads of key highways leading west to Damascus and Homs, and east to Iraq.