Damascus (AFP) - Syria and its ally Russia said Saturday that dozens of civilians and rebels had left besieged eastern Aleppo through humanitarian corridors but residents there and rebels dismissed the claims as "lies".

The reported crossings came 48 hours after Russia announced safe passages to allow evacuations from the rebel-held eastern areas, where an estimated 250,000 people are under government siege and facing food shortages.

State television broadcast footage it said showed women and children crossing into the government-held part of Salaheddin neighbourhood, under the watch of soldiers.

"This morning dozens of families left via the corridors identified... to allow the exit of citizens besieged by terrorist groups in the eastern neighbourhoods," state news agency SANA reported.

"They were welcomed by members of the army and taken by bus to temporary shelters," it added.

It said that "a number" of women over the age of 40 had left in addition to the families and were also taken to shelters.

"Armed men from eastern neighbourhoods of Aleppo" turned themselves over to army soldiers in Salaheddin district, SANA said without giving further details.

State television broadcast footage of a few men entering government territory carrying their weapons aloft, some with scarves wrapped around their faces.

Russia's defence ministry said that 169 civilians had crossed into the government-held west of the city since Thursday.

It added that 69 rebels had laid down arms and said another four crossings would be opened to allow more evacuations.

- Rebels say evacuations are 'lies' -

But on the ground, residents and an AFP correspondent said there was no sign of movement, adding that makeshift berms were still in place across the road from rebel to regime territory in Salaheddin.

The Syrian Observatory for Human Rights, a Britain-based monitor, said around 20 people had crossed from the east into the west, but insisted none were rebels.

"The regime claimed today that they opened the crossings towards Salaheddin, and this is all hearsay and lies," said Iyat Abu Mohamed, a commander with the Nureddin al-Zinki rebel group.

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"We're standing here by the Bustan al-Qasr crossing. The regime is lying," local rebel commander Yasser Flis told an AFP correspondent in Aleppo.

"They didn't open any crossing or implement a truce at the crossing... on the contrary, they've increased their air strikes and shelling of the crossing," he said.

Once Syria's economic powerhouse, Aleppo has been ravaged by the war that began in March 2011 with anti-government protests.

It has been roughly divided between government control in the west and rebel control in the east since mid-2012.

Eastern neighbourhoods have been under total siege since July 17, when government forces seized the opposition's only remaining supply route.

The siege has led to food shortages and spiralling prices, and aid agencies have warned that residents risk starvation.

- Afraid to leave -

But the humanitarian corridors announced by Russia have been met with suspicion by residents, as well as countries including the United States.

On Friday, US Secretary of State John Kerry said the initiative could sour cooperation with Russia on Syria if it turned out to be a "ruse".

And the White House said it was "sceptical".

Many residents said they were afraid to cross into regime-held territory from government-controlled routes.

"I want to leave, but not to government-held areas," said Abu Mohamed, a 50-year-old father of four living in Al-Shaar district.

"I'm very afraid that they will take my 17-year-old son and force him to sign up for military service and send him to the frontlines," he told AFP.

"The humanitarian situation is more and more desperate and it's hard to find food," he added.

The UN voiced provisional support for the idea, but asked for control of the routes.

"Our suggestion to Russia is to actually leave the corridors being established at their initiative to us," UN envoy Staffan de Mistura said Friday.

"How can you expect people to want to walk through a corridor, thousands of them, while there is shelling, bombing, fighting?"

On Saturday, regime warplanes continued to hit opposition targets, with the Observatory reporting air strikes on two rebel-held areas on the outskirts of Aleppo.

It also reported clashes in the two neighbourhoods, saying the government was attempting to forestall any rebel bid to bring in reinforcements to try to break the regime siege.