* Syrian army says corridors opened for rebels and civilians
* Rebels say preparations under way for major assault on army

The Syrian military said on Thursday a unilateral ceasefire backed by Russia had come into force to allow people to leave besieged eastern Aleppo, a move that the rebels have said is part of a psychological campaign to get them to surrender.

State media earlier said the army had opened exit corridors in two designated areas in the Bustan al Qasr quarter and near the Castello road in northern Aleppo city. Waiting buses were shown on state television.

Intensified Russian and Syrian bombing of besieged rebel-held parts of Aleppo in the past weeks has hit hospitals, bakeries and water pumping stations, and killed hundreds of civilians.

The United Nations has criticised unilateral ceasefires after long sieges, saying they can be helpful only if combined with humanitarian access for those who do not want to leave.

The 250,000 civilians trapped inside the besieged rebel held parts of the city have so far stayed away from the corridors. The army blames rebels opposed to President Bashar al-Assad for preventing them leaving and says they use civilians as human shields.

Rebels say the goal of Moscow and Assad is to empty rebel-held areas of civilians so they can take over the whole city.

‘They talk about humanitarian corridors, but why are they not allowing food into besieged eastern Aleppo to alleviate our suffering? We only need the Russian bombers to stop killing our children. We don't want to leave,’ said Ammar al Qaran, a resident in Sakhour district.

State owned Ikhbariyah television said rebels had fired a barrage of mortars near to where ambulances had been heading to take patients from the besieged parts of the city for treatment in government-held areas.

MEDICAL TREATMENT

The Syrian military said on Wednesday it would observe the temporary ceasefire to allow trapped civilians to escape and said it had pulled back to enable rebel fighters to leave the city via two designated corridors.

‘We guarantee a safe exit. Seize the opportunity and save your families,’ an army loudspeaker blared near an exit corridor, on live footage shown on the pro-Syrian government Lebanese news channel Mayadeen.

‘An appeal to our people ... we will extend every help from shelters to hot dishes and facilities that offer you medical treatment,’ said the army loudspeaker.

To the rebels, the army broadcaster said: ‘Drop your weapons, this is your last chance.’

Since Russia intervened in the war a year ago, the government's side has gained the upper hand on numerous fronts, including Aleppo, where the opposition-held sector has been completely encircled for weeks.

The Syrian army has pressed ahead with a major campaign, supported by Iranian-backed militias and Russian air power, to take full control of Syria's largest city, divided between rebel and government zones since 2012.

The rebels, however, say they are preparing a large-scale offensive to break the siege of Aleppo and that the Russian air force has failed.

‘The coming battle is not going to be like others. We are waiting for the signal of the start of a decisive battle which will surprise the regime and its militias,’ Abu Obeida al Ansari, a commander from Jabhat Fateh al-Sham, the rebranded former al Qaeda affiliate Nusra Front, said in a statement on social media.