"The 'regime of silence' in Aleppo and its province has been extended by 48 hours from Tuesday 01:00 am (local time) to midnight on Wednesday," a statement early Tuesday said.

The temporary truce, initially for two days and then prolonged until Tuesday at 00:01 am (21:01 GMT Monday), was decided after fighting killed nearly 300 people since April 22 in Aleppo, where some areas are held by opposition and others by government forces.

The announcement came as Russia and the United States agreed to boost efforts to find a political solution to Syria's five-year war which has killed more than 270,000 people and displaced millions, according to AFP.

The two powers also agreed to extend a truce across the whole of the country.

"The Russian Federation and United States are determined to redouble efforts to reach a political settlement of the Syrian conflict," according to a joint US-Russian statement published by the Russian foreign ministry.

To this end, Russia "will work with the Syrian authorities to minimize aviation operations over areas that are predominantly inhabited by civilians or parties" to the ceasefire, it said.

The two powers brokered a February 27 ceasefire between the government and the armed opposition that did not, however, include terrorist fighters such as the Daesh (ISIL) group and Al-Qaeda's Syria affiliate, Al-Nusra Front.

On Sunday, armed opposition groups fired rockets into a government-held district of Aleppo, killing five civilians including two children.