Commanders of various opposition groups said on Saturday that government shelling continued in many parts of Syria in what they described as a violation of a cessation of hostilities agreement. The ceasefire agreement entered into force at midnight under a US-Russia plan which the United Nations has called the best hope for peace in the five-year conflict. Fares Bayoush, head of the Fursan Al-Haqq group which fights under the banner of the Free Syrian Army, told Reuters that continued violations could lead to a collapse in the agreement. "There are areas where the bombardment has stopped but there are areas where there are violations by the regime such as Kafr Zeita in Hama, via targeting with artillery, and likewise in Morek in northern Hama countryside," he said, adding that FSA groups remain committed to the truce. Bayoush said it was normal for violations to take place in any truce but the other side should halt them if it was serious about the agreement. "But if these violations continue they may lead to the collapse of the agreement," he said. Jaish Al-Islam opposition group also said government forces dropped two barrel bombs and opened fire on its positions during several violations of a cessation of hostilities agreement in the Eastern Ghouta near Damascus on Saturday. Citing field reports from the group's commanders, Jaish Al-Islam spokesman Islam Alloush told Reuters that in one incident government forces trying to advance "were dealt with with machine guns." The cease-fire went into effect across Syria early Saturday, marking the biggest international push to reduce violence in the country's devastating conflict that has killed 250,000 people, wounded a million and created Europe's worst refugee crisis since World War II. The truce does not include either the Daesh group or Al-Qaeda's branch in Syria, known as the Nusra Front. Meanwhile, a suicide car bomb exploded Saturday on the edge of a government-held central town, killing two people and wounding four. No one claimed responsibility for the blast on the eastern entrance of the town of Salamiyeh. The Britain-based Syrian Observatory for human Rights said the explosion was the work of Daesh, adding that the two killed were both soldiers. It added that Syrian warplanes' attacked suspected Daesh positions in areas outside Salamiyeh. The Observatory said intense fighting is ongoing near the northern town of Khanaser between troops and pro-government gunmen against Daesh. Battles have been ongoing for five days in the strategic area that that is close to the highway that links Aleppo with central and western Syria.