Women walk on rubble in al-Shadadi town in Hasaka province, Syria on 26 February Rodi Said/Reuters

At least two people have been killed after a car bomb was detonated in a government-held town in Syria. The explosion occurred a few hours after a ceasefire brokered by the US and Russia came into effect at 10.00pm GMT on 26 February.

No group has claimed responsibility for the explosion in Salamiyeh, western Syria. While the truce applies to government and rebel forces, it does not include the Islamic State (Isis) and the al-Qaeda backed Nusra Front.

Britain-based Syrian Observatory for Human Rights (SOHR) said that since the truce kicked in there has been relative calm in many parts of the country. It also claimed that the car bomb was carried out by Isis (Daesh).

"The car bomb attack is not a breach to the truce because it occurred in an area where the cessation of hostilities agreement does not apply," SOHR's Rami Abdulrahman told Reuters. Salamiyeh is a frontline between IS and government forces.

Assad forces 'barrel bomb' attack

Rebel group Jaish al-Islam claimed that government forces have already violated the ceasefire after dropping two barrel bombs and opening fire on its positions in Eastern Ghouta, near Damascus. Speaking to Reuters and referring to field reports from group commanders, Jaish al-Islam spokesman Islam Alloush said advancing government forces "were dealt with with machine guns".

Staffan de Mistura, the UN Special Envoy for Syria said that violence had "calmed down". He added that one violation was being investigated.

De Mistura said: "Let's pray that this works because frankly this is the best opportunity we can imagine the Syrian people has had for the last five years in order to see something better and hopefully something related to peace". Syria's civil war has claimed more than 250,000 lives and injured a million others. Around 11 million Syrians have been forced from their homes, of which four million have sought refuge abroad.

In the run-up to the ceasefire, US President Barack Obama warned the Syrian government and key ally Russia that "the world will be watching". The UN said that it expected breaches in the temporary cessation of hostilities and appealed for restraint.