An opposition group fighting under the Free Syrian Army banner in northwest Syria has withdrawn from a shaky nationwide ceasefire, blaming the Assad regime and its allies for violations."Due to Russia's lack of commitment as a guarantor...we announce that, as of today, we are not bound by this agreement," Jaish al-Ezza, a signatory to the deal brokered by Russia and Turkey, said in a statement on Sunday.

The group said its decision was in response to what it described as heavy Russian bombardment of its positions and surrounding areas in Hama province.

Fighting and air strikes have plagued the ceasefire between the government and opposition groups since it took effect in late December, with the combatants accusing each other of violations.After two days of negotiations in Kazakhstan last week, Russia, Turkey, and Iran agreed to ensure full compliance with the fragile truce.Jaish al Ezza, which has received foreign aid from states opposed to the Assad regime, also blamed government forces and allied militia for breaching the ceasefire in Wadi Barada near Damascus.A month-long offensive against opposition groups in Wadi Barada ended on Sunday when the government captured the valley, where a major spring supplies most of the capital's water.The Hama-based opposition group's withdrawal from the truce could further complicate the battlefield in the insurgent-held northwestern corner of Syria, where radicals and more moderate factions are at war with each other.The Syrian conflict pits Assad's regime, backed by Russia and Iran, against an array of opposition groups, including some supported by Turkey, Gulf monarchies, and the United States.

Despite an overall reduction in violence, more than 400 civilians have died in clashes and bombardment since the truce began, the Syrian Observatory for Human Rights war monitor said.