Russian and Syrian warplanes stopped conducting airstrikes on the besieged Syrian city of Aleppo on Tuesday ahead of a planned 8-hour, temporary truce on Thursday.

According to Russia's state-run Tass news agency, Russian Defense Minister Sergei Shoigu said that the cessation of air raids was necessary to allow Russia to carry out a "humanitarian pause" during which people could leave the rebel-held area via special corridors.

Pro-opposition activists denied, however, that these corridors exist, saying civilians continue to be trapped in the city.

"The people in besieged eastern Aleppo will not use a corridor only supervised by Russia and the regime," Rami Abdel Rahman, the head of the Britain-based Syrian Observatory for Human Rights, told the German DPA news agency.

"They want a corridor supervised by the UN," he added.

The UN has previously said that people in eastern Aleppo were afraid of leaving the city through the government-designated safe passages, noting that Syrian army units were stationed at the crossings.

Russian President Vladimir Putin's spokesman, Dmitry Peskov, meanwhile said that the halt in the airstrikes came as a goodwill gesture, saying he hoped "that our partners will allow us all to take advantage of that."

Russian and Syrian officials embraced a proposal made earlier this month by the UN Syria envoy, Staffan de Mistura, to allow al-Qaida-linked militants to leave Aleppo in exchange for a truce. De Mistura said earlier that east Aleppo might face complete destruction by the end of the year in the absence of a ceasefire.

Rebels and many residents have repeatedly rejected the plan.

The majority of residents have reportedly rejected the truce proposed by UN Syria envoy Staffan de Mistura

Dire situation in Aleppo

Russia started its intervention in Syria about 12 months ago in a boost to President Bashar al-Assad's army, which has gradually been collapsing after fighting rebel forces for five years. Russia's air campaign has enabled Syrian government forces to reclaim territory from both moderate rebels as well as the self-styled "Islamic State" extremist group (IS).

Aleppo, Syria's largest city, has been subjected to the most intense aerial bombardment since the start of the country's conflict in 2011. In recent months, the Syrian army has pressed its offensive into the rebel-held eastern part of the city.

Some 250,000 to 300,000 civilians are thought to be trapped in eastern Aleppo, which has been suffering from dwindling food supplies and extremely limited medical care. Hospitals have repeatedly been targeted in recent airstrikes, prompting a number of Western governments to raise calls for investigations into war crimes.

UN still unable to move in

Meanwhile the UN said that it had not yet received the required security guarantees to be able to carry out humanitarian work in Aleppo when the "humanitarian pause" comes into effect. The UN and other aid organizations have repeatedly had to face obstacles and outright attacks in the past in trying to reach those in Aleppo, who need humanitarian aid the most.

"We need all assurances before we can do anything meaningful – such as evacuating the sick and wounded and to bring anything into the city which has been under siege," says Jens Laerke of the UN Office for the Coordination of Humanitarian Affairs (OCHA).

"So far, we have not received assurances from all sides," he added.

"When the weapons fall silent, we need all weapons to fall silent. We need assurances from all parties to the conflict, not just a unilateral announcement that this will happen."

ss/jm (AP, dpa, Reuters)