Russian and Syrian regime warplanes Friday intensified air strikes across Syria, just hours before a US-Russian-brokered ceasefire is to go into effect, a monitoring group said.
"Planes believed to be Russian have intensified their strikes since midnight on rebel-held posts," the head of the Syrian Observatory for Human Rights, Rami Abdel Rahman, told dpa.
The attacks focused on the northern sectors of Latakia province on the coast, the north-western Idlib province, western and northern Aleppo province and the northern outskirts of Hama province.
Abdel Rahman added that at least 35 raids, also believed to be Russian, targeted areas in the Ghouta and Douma regions on the outskirts of the capital Damascus. The southern province Daraa was also hit.
Despite concerns over the ceasefire deal's pitfalls, including doubts about the Syrian government's sincerity and the exclusion of hardline Islamic rebel fighters, the deal is expected to go into effect at midnight Damascus time (2200 GMT).
The deadline for armed groups to sign up to the ceasefire passed at noon Damascus time.
The Syrian government confirmed its participation earlier this week as did the Kurdish People's Protection Units (YPG). The opposition Southern Front and other Free Syrian Army factions have also joined.
The full extent of participation remains unclear. The deal excludes the Islamic State group, the al-Qaeda affiliated al-Nusra Front and other UN-listed terrorist groups, but disputes remain as to which groups are affiliated with which and where each are located.
Turkey, a neighbour of Syria and a major rebel backer, has expressed doubts about the ceasefire, noting the latest round of Russian airstrikes as well as gains in the country by their perennial foes the Kurdish militants.
US President Barak Obama, acknowledging such scepticism, described the situation in both Syria and Iraq as "one of the most complex the world has seen in recent times."
"The fight in Syria is not only a civil war but it is also a proxy war between regional powers reflecting deep sectarian and political rivalries," Obama said, adding that he was determined to give diplomacy a chance while at the same time vowing to keep up the aerial campaign against Islamic State.
In New York, the 15-member UN Security Council is set to meet at 2000 GMT to hear a briefing from UN Syrian envoy Staffan de Mistura, a UN statement said. De Mistura has indicated he is planning a new round of peace talks to build on the ceasefire.
According to reports the council is expected to also vote Friday on the draft resolution endorsing the ceasefire.
Meanwhile, a source in the Russian Foreign Ministry cited by the country's Interfax news agency said Friday that peace negotiations could resume on March 7 in Geneva.
The agency went on to quote Syrian spokesman of the opposition bloc High Negotiations Committee as saying the opposition was ready to resume talks with the Syrian government on that day.
"We want nothing to interfere with this happening because, in principle, we are ready," said Riyad Naasan Agha.