BEIRUT (Alliance News) - Russian and Syrian warplanes intensified airstrikes across Syria, a monitoring group said, hours before a ceasefire brokered by Washington and Moscow was to go into effect.
The "cessation of hostilities" deal was scheduled to begin at midnight Damascus time (2200 GMT Friday).
The opposition announced at the last minute that 97 rebel factions have signed up to the ceasefire, and also expressed deep concerns that the truce would be "exploited" by the government.
The head of the Syrian Observatory for Human Rights, Rami Abdel Rahman, told dpa that "planes believed to be Russian have intensified their strikes since midnight on rebel-held posts."
The areas targeted included northern sectors of the coastal province of Latakia, north-western Idlib province, western and northern parts of Aleppo province and the northern outskirts of Hama province.
Abdel Rahman said at least 40 air raids, also believed to be Russian, hit the areas of Ghouta and Douma on the outskirts of the capital Damascus. The southern province of Daraa was also attacked.
The ceasefire agreement excludes Islamic State, Syrian al-Qaeda affiliate the al-Nusra Front and other UN-listed terrorist groups.
In many areas, al-Nusra Front fights alongside rebels, raising the possibility that groups who agreed to adhere to the truce might still be targeted by the Syrian government or Russia.
The leader of al-Nusra Front rejected the truce call and urged rebel groups to "intensify" attacks against the Syrian government, in an address on pro-opposition Orient TV.
Russian President Vladimir Putin said his air force will continue bombing UN-designated terrorist groups in Syria.
The ceasefire "does not include Islamic State, al-Nusra Front and other terrorist organizations recognized as such by the UN Security Council," he said, according to state news agency TASS.
Meanwhile, Syrian President Bashar al-Assad's troops regained control of the sole supply route to government-held areas in the northern city of Aleppo from Islamic State.
"The government troops regained all hills and the key supply route linking Aleppo with the town of Khanasser to its south-east," Abdel Rahman said. Khanasser was the only lifeline to government-held parts of Aleppo.
On Thursday, US President Barack Obama said there were no illusions about the ceasefire and there were many reasons for scepticism.
"If implemented - and that's a significant 'if' - this cessation could reduce the violence and get more food and aid to Syrians who are suffering and desperately need it," he said.
"It could also lead to negotiations on a political settlement to end the civil war so that everybody can focus their attention on destroying [Islamic State]," Obama said, adding that "I want to make totally clear that there will be absolutely no ceasefire with respect to [Islamic State]."
At 2000 GMT, the UN Security Council will hear from UN Syrian envoy Staffan de Mistura, who has indicated that he is planning a new round of peace talks to build on the ceasefire.
A source in the Russian Foreign Ministry said peace negotiations could resume on March 7 in Geneva, according to Interfax news agency.