Russia and the Syrian government are beginning a massive humanitarian operation in the besieged northern city of Aleppo, Russian Defence Minister Sergei Shoigu said Thursday.
The operation aimed at helping the civilian population will also provide assistance to militants who surrender their weapons, Shoigu said, according to Russian state news agency TASS.
An estimated 250,000 to 300,000 civilians are thought to remain in Aleppo's opposition-held sector where government forces have imposed a tight siege after blocking all supply routes.
The Syrian government opened three humanitarian corridors for residents willing to leave the rebel-held neighbourhoods, Aleppo Governor Mohammed Marwan said.
They will be provided with temporary accommodation, he told Syrian state news agency SANA.
An unspecified number of people left through one corridor for regime-controlled neighbourhoods in western Aleppo, a monitoring group said.
According to the Syrian Observatory for Human Rights, government helicopters dropped leaflets with maps showing the exit routes.
The International Committee of the Red Cross (ICRC) said the corridors must ensure the safety and respect to all civilians, regardless of whether they decide to leave.
Any effort to provide "civilians some respite from the ongoing and indiscriminate violence, and allows them to voluntarily leave for safer areas, would be much welcomed", ICRC's Robert Mardini said.
However, he said corridors "have to be implemented with the consent of parties on all sides."
Activist Mahmoud al-Shami, who is based in eastern Aleppo, told dpa via Facebook that residents inside the city see the initiative as a "propaganda ploy" by President Bashar al-Assad's regime and Moscow.
"They want us to leave and then they will arrest all of us," al-Shami added.
The United Nations said it was surprised by the humanitarian corridors. "We were not consulted," UN Syria envoy Staffan de Mistura told reporters in Geneva.
UN humanitarian affairs chief Stephen O'Brien said the security of humanitarian corridors must be guaranteed by all parties and their use should be voluntary.
"No one can be forced to flee, by any specific route or to any particular location," O'Brien said. "Protection must be guaranteed for all according to the principles of neutrality and impartiality."
Samantha Power, US ambassador to the UN, posted a letter to Twitter sent by Syria's ambassador to the UN Security Council that said the Syrian army had informed eastern Aleppo residents of the safe passages and accommodation to those deciding to leave.
Power called the letter "chilling," and said via Twitter that the Syrian UN ambassador "warns Syrians to leave E Aleppo & entrust lives to gov that's bombed & starved them."
Matthew Rycroft, British ambassador to the UN, was guardedly optimistic about the Russian proposal, saying Britain "would welcome it if it were a humanitarian initiative ... let's very much hope and insist that it is."
On Tuesday, Syrian state media reported that government forces had called on civilians and rebel fighters to leave eastern Aleppo, after they had blocked Castello Road, the last route into opposition-held districts in the city earlier this month.
In Paris, the French and British foreign ministers called for ending the siege of Aleppo before Syria peace negotiations can start again.
French Foreign Minister Jean-Marc Ayrault and his British counterpart Boris Johnson said Moscow must wield its influence to restart peace negotiations as "only Russia has the ability to convince Bashar al-Assad's regime to end the war and return to the negotiating table."
Aleppo, Syria's largest city before the war, has been divided between the government-held west and the rebel-held east since mid-2012.
Regime forces have made gains against the rebels since Russia started an air campaign in Syria in support of al-Assad in September 2015.
Al-Assad on Thursday offered an amnesty to rebels who surrender in the next three months, SANA reported.
In power since 2000, al-Assad has portrayed his deadly crackdown on the opposition as a "war on terrorism."
Meanwhile, Human Rights Watch accused al-Assad and his Russian allies of "extensively" using the widely banned cluster munitions on rebel-held areas.
The group said that it had documented 47 cluster munition attacks that killed and injured dozens of civilians in opposition-controlled territory across three Syrian provinces over the past two months.