The jihadis have now advanced to “500 meters away from the entrance of Hassakeh, after fierce clashes against regime forces south of the city,” said Rami Abdel-Rahman, director of Britain-based monitoring group the Syrian Observatory for Human Rights.

He said ISIS had seized all military posts in that area of northeastern Syria, including an unfinished prison building and a power plant, after at least six suicide bombers struck Wednesday.

Regime helicopters meanwhile dropped barrel bombs on jihadi positions, he said.

Control of Hassakeh city is split between regime and Kurdish forces, who have fought ISIS elsewhere in the province.

If ISIS seizes Hassakeh it would be the second Syrian provincial capital to fall under its control, after Raqqa, the group’s bastion to the west.

It would also be the third provincial capital lost by the regime. The northwestern city of Idlib was seized by rebels in March.

Fighting Wednesday around Hassakeh left 27 regime fighters and 26 jihadis dead, the Observatory said.

All electricity and methods of communications in Hassakeh city have been cut off, said activist Arin Shekhmos, citing residents who fled the provincial capital.

Other residents have moved to the northern and western Kurdish-controlled parts of Hassakeh city following ISIS mortar fire, he told AFP from the city of Qamishli.

The Al-Watan newspaper, which is close to the government, said ISIS had begun a “violent attack on Hassakeh” but criticized Kurdish forces for failing to support regime troops.

Local activists in Hassakeh have said the Kurdish YPG militia has been engaged in a concerted drive to round up young men for military service, as the assault continues.

ISIS began its assault on Hassakeh on May 30 and launched a simultaneous offensive against rebels in Aleppo province.