The Syrian army has unilaterally extended a nationwide ceasefire for three days, while residents of besieged Aleppo face food and fuel shortages after government forces cut off a primary supply route.

The Syrian army announced a 72-hour ceasefire extension on Saturday, the government-run SANA news agency reported. The ceasefire, which started on Wednesday, was marred by violations from all sides.

The Free Syrian Army (FSA), an opposition group, said it would honour the ceasefire.

In northern Syria's Aleppo, at least 43 civilians have been killed in fighting in recent days. The United Kingdom-based Syrian Observatory for Human Rights said rebel shelling on government-controlled parts of the city killed 34 civilians, while government air strikes on the rebel-held eastern Aleppo left nine dead.

"Over the past few days, there has been no ceasefire on the ground," Al Jazeera's Zeina Khodr reported from Kilis, Turkey. "On the ground, there is no truce and the violence continues."

The Russian Ministry of Defence said on Saturday that the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) armed group shot down a military helicopter near Palmyra, killing two Russian pilots.

Fear of shortages

Around 200,000 people remain in the opposition-held eastern sectors of Aleppo, which has been divided between government and rebel control since shortly after fighting in the city began in mid-2012.

Residents there described shortages of basic goods after government troops advanced within firing range of the key Castello Road supply route.

"For two days the situation was calm. I went to the market and I filled up my motorbike with gasoline. Today, I couldn't even find a single tomato," said Bilal Qaterji, a local textile factory employee.

"There's not a drop of fuel left because the Castello Road has been cut," he told AFP.

Government troops effectively severed the Castello Road on Thursday with the capture of a hilltop within firing range of the key route.

On Friday, at least 22 people were killed by air strikes on a market in the western part of the Idlib province

More than 270,000 Syrians have been killed since the conflict began in March 2011. Although it initially started as a largely unarmed uprising against President Bashar al-Assad, it quickly turned into a full-scale civil war.