A fighter from the Syrian rebel group Jabhat al-Nusra rides a motorcycle along a deserted street in Deir al-Zor August 17, 2013. REUTERS/Khalil Ashawi

The head of Syria’s branch of al-Qaeda, one of its most powerful rebel groups, called for an escalation in fighting against the government and its allies on Saturday and urged opponents of President Bashar al-Assad to reject a ceasefire due to begin at midnight.

The government and the opposition have agreed to take part in a U.S.-Russian “cessation of hostilities” accord that is due to begin at midnight (2200 GMT on Friday). Warring parties had been required to sign up by noon.

Under the measure, which has not been signed by the Syrian warring parties themselves and is less binding than a formal ceasefire, the government and its enemies are expected to stop shooting so aid can reach civilians and peace talks begin.

The truce excludes jihadist groups such as ISIS and the al-Qaeda-linked Nusra Front. The Damascus government and its Russian allies said they will not halt operations against those militants.

The Nusra Front on Friday urged insurgent groups to intensify their attacks against President Bashar al-Assad and his allies.

“Beware of this trick from the West and America because everyone is pushing you to go back under the thumb of the oppressive regime,” Mohammad al-Jolani, the head of Al-Nusra Front, said in an audio message on Orient News TV released on Friday.

“Strengthen your resolve and intensify your strikes, and do not let their planes and great numbers (of troops) scare you”, al-Jolani added.

Unlike ISIS, which controls defined areas of territory in central and eastern Syria, the Nusra Front is widely disseminated in opposition-held areas in the west, and any escalation would increase the risks of the truce collapsing.

Nusra is bigger than nearly all the factions taking part in the cessation, with fighters across western Syria.
As the deadline for the cessation of hostilities drew nearer, heavy air strikes were reported to have hit opposition-held areas near Damascus while fighting raged across much of western Syria.

The Syrian government has agreed to the cessation plan. The main opposition alliance, which has deep reservations, said it would accept it for two weeks but feared the government and its allies would abuse it to attack opposition factions under the pretext that they were jihadists.

Russian news agencies reported that President Vladimir Putin saying that Russia had received information confirming that all parties expected to take part in the cessation of hostilities were ready to do so.

Putin reasserted the continuous combat actions against ISIS, the Nusra Front and other groups which the Syrian government regards as terrorists.

“I would like to express the hope that our American partners will also bear this in mind … and that nobody will forget that there are other terrorist organizations apart from ISIS,” he said in Moscow.