Syria rebels say attacks by army and Russian planes threaten truce

The agreement, which is in its second day and has drastically curbed violence but not stopped it entirely, is the first of its kind to be attempted in four years.

In a letter to UN Secretary-General Ban Ki-moon, the opposition said violations would undermine international efforts to guarantee the continuation of the truce and lead to the collapse of the UN-adopted political process.

The Riyadh-based opposition body said Russian war planes on February 28 staged 26 bombing raids on areas where rebel groups abiding by the truce were operating and accused Moscow of deploying cluster bombs on residential areas it alleged caused many civilian casualties.

Under the accord accepted by President Bashar al-Assad's government and many of his foes, fighting should cease so that aid can reach civilians and talks can open to end a war that has killed more than 250,000 people and made 11 million homeless.

The head of the Russian coordination center in Syria, Sergei Kuralenko, said the plan was holding "in general" but said there had been nine violations of the truce in the past 24 hours.

Insurgents and the Britain-based Syrian Observatory for Human Rights, which monitors the conflict, said war planes struck at least six towns and villages in west and north Aleppo and a village in the central Hama province.

Warplanes believed to be Russian pounded the town of Teir Maalah, just north of the city of Homs, in the second round of bombing within a few hours of the strategic town that the army has tried to capture in the past to enter rebel held northern countryside of Homs province, insurgents said.

Rebels said the attacks across Syria were more intense than February 27 but still not as bad as those before the cessation of hostilities took effect.

"We are awaiting the response of states to these violations, the situation is in the balance now and self restraint will not last long," colonel Fares al Bayoush told Reuters.

The Saudi-backed opposition group had earlier accused Russia of carrying out the strikes and said it would complain to the United Nations and countries backing the peace process but said it remained committed to the truce.

Saudi Foreign Minister Adel al-Jubeir also accused Russia and the Syrian government air force of violating the truce and said Riyadh was discussing the issue with international powers.

Muslat, who is spokesman for the opposition's High Negotiating Committee (HNC), said it was waiting for answers about how the cessation of hostilities in Syria was being monitored, particularly since there was no map with a common understanding of the location of various fighting groups.