Aleppo - Syria regime ally Russia on Thursday announced a "large-scale" aid operation to allow civilians and fighters to flee besieged Aleppo, as the president offered an amnesty to rebels who surrender.Government forces have surrounded rebel-held districts in eastern Aleppo since July 17, sparking fears for at least 200 000 people who live there.Residents have reported food shortages and spiralling prices in rebel districts since regime forces cut off the opposition's main supply route into the northern city earlier this month. Russian Defence Minister Sergei Shoigu said three humanitarian corridors were being opened "to aid civilians held hostage by terrorists and for fighters wishing to lay down their arms".He told Russian news agencies that a fourth corridor would be opened to the north of Aleppo for rebels to flee with their weapons.Medical and food assistance would be provided along the routes for civilians and fighters who lay down their weapons, Shoigu said, adding the operation would get underway later on Thursday.President Bashar Assad, meanwhile, issued a decree offering an amnesty to rebels who surrender over the next three months, the official SANA news agency reported.Smoke billows from buildings during an operation by Syrian government forces to retake control of the rebel-held district of Leramun, on the northwest outskirts of Aleppo. (George Ourfalian, AFP) "Everyone carrying arms... and sought by justice... is excluded from full punishment if they hand themselves in and lay down their weapons," SANA reported.Syria's state broadcaster also announced "the opening of three passages to allow citizens out of eastern districts" of Aleppo.But an AFP correspondent who went to see one of the corridors said it remained closed and saw no movement of residents nearby. Regime planes on Thursday dropped flyers showing a map with the location of these humanitarian passages, he said, as well as small aid packages.As Russia made the announcement, France and Britain renewed demands for an end to the regime's "disastrous" siege of eastern Aleppo.French Foreign Minister Jean-Marc Ayrault and his British counterpart Boris Johnson, in a joint statement, said the consequences of the siege, "including the bombardment of civilians and medical facilities, are already disastrous and could generate further refugees".Regime advance Previously the country's economic hub, Aleppo and its surrounding countryside have suffered some of the worst fighting in the five-year conflict that has killed more than 280,000 people.It has been roughly divided into a regime-controlled west and a rebel-held east since July 2012.Analysts say that losing Aleppo would be a major blow for the armed opposition and could signal a turning point in the conflict, which began in 2011 with the brutal crackdown of anti-government protests.Also on Thursday, Syrian government forces drove rebels from the neighbourhood of Bani Zeid, on Aleppo's northern outskirts, after heavy overnight fighting, a monitor said.The Britain-based Syrian Observatory for Human Rights said the capture of Bani Zeid further tightens the regime siege of rebel-held districts.UN envoy Staffan de Mistura said the world body had not been consulted on Russia's initiative, warning that the humanitarian situation was "very serious" in eastern Aleppo which had only two to three weeks worth of supplies.On the political front, the envoy has said he hopes that peace talks aimed at finding a solution to end the Syria war could resume at the end of August.Meanwhile, Human Rights Watch on Thursday accused Assad's regime and Russia of extensively using banned cluster munitions against the rebels since late May. The New York-based watchdog said it had documented 47 cluster munition attacks that killed and injured dozens of civilians in rebel-held areas in three provinces since May 27, many north and west of Aleppo.Widely banned, cluster munitions contain dozens or hundreds of bomblets and are fired in rockets or dropped from the air.They spread explosives over large areas and are indiscriminate in nature, often continuing to maim and kill long after the initial attack when previously unexploded bomblets detonate.