MOSCOW (AP) — Russia and the Syrian government said they will open humanitarian corridors in Syria's embattled city of Aleppo on Thursday and offer a way out for opposition fighters wanting to lay down their arms, even as Syrian forces took another district from rebels in the city.

The Russian announcement by Defense Minister Sergei Shoigu came as Syria's President Bashar Assad offered a general amnesty for rebels who give up their weapons and surrender to authorities over the next three months.

Rebels and residents of Aleppo said they were deeply skeptical of the offer, and there was no immediate sign of people massing to leave the besieged parts of the city.

Rights groups said opening safe passages to civilians trapped in eastern Aleppo city won't avert a catastrophe and does not give Syrian and Russian forces carte blanche to further blockade the opposition-controlled territory.

In a statement Thursday, the London-based Amnesty International said providing safe routes for those civilians wishing to leave is "no substitute for allowing impartial humanitarian relief for civilians who remain in opposition-held areas," many of whom will be skeptical about government and Russian promises.

"Providing safe routes for those civilians who wish to flee Aleppo city will not avert a humanitarian catastrophe," said Philip Luther, director of the Middle East and North Africa program for Amnesty.

"The fact that you provide this option doesn't mean that the people who stay behind are legitimate military targets," said Nadim Houry, the deputy Middle East director at Human Rights Watch, in comments to The Associated Press.

For days now, Syrian government forces and allied troops have encircled the main rebel enclave in Aleppo, urging fighters there to surrender. The encirclement set the stage for a prolonged siege that the government hopes will eventually force the rebels to surrender, a tactic Assad's forces have used elsewhere, including in the central city of Homs.

But humanitarian groups have warned of a major catastrophe if the siege on the rebel-held parts of Aleppo continues. Some 300,000 residents are trapped in the eastern part of the city that is controlled by rebels, according to the United Nations.

Shoigu said in televised comments that President Vladimir Putin has ordered a "large-scale humanitarian operation" that will be launched outside Aleppo to help civilians as well as allow fighters who wanted to lay down the arms to surrender.

He said three corridors will be open for civilians and fighters who lay down their arms and a fourth corridor providing fighters a "safe exit with weapons."

"Given the fact that our American counterparts have not provided intelligence about the Nusra Front and Syrian Free Army squads (we) will create a fourth corridor for a safe exist with weapons in the north of Aleppo in the direction of the Castello highway," he said. The Nusra Front is al-Qaida's branch in Syria while the Syrian Free Army is the name of the main Western-backed rebels. Both have fighters in Aleppo.

The U.N. envoy for Syria, Staffan de Mistura, said he wants to see how the United Nations could coordinate with Russia on its plan to help civilians and opposition fighters who lay down their weapons outside Aleppo, which he called "de-facto" besieged.

"In Aleppo, the situation is extremely serious, no doubt," de Mistura said. "There is probably — we heard — two to three weeks of supplies, and in view of the bombing of the warehouses, medical facilities, bakeries, and the need of treating wounded people when in fact medical facilities are being hit, the humanitarian situation is getting more and more concerning."

Meanwhile, the governor of Aleppo province, Mohammed Olbi, said three crossings have been opened for residents, adding that those who leave would be given temporary accommodation. Syrian TV said fliers have already been dropped on rebel-held areas of Aleppo urging people to take the government's offer of humanitarian corridors. The TV also aired a call from Aleppo clerics, calling on armed groups to drop their weapons.

There were no immediate signs of people converging on the crossings.

Bahaa Halabi, an opposition media activist inside Aleppo, said there are no corridors out of east Aleppo and even if there were, he would not take them.

"Definitely not. We will not surrender ourselves to the criminals. They are killing us every day. Slaughtering us, starving us, and besieging civilians," he said, speaking from the city via Skype.

Fliers dropped on eastern Aleppo show corridors to government areas, according to Ibrahim Haj, who directs the media office. He said some families may send their women and children through the corridors but not men. Also, he said there is clearly little confidence in the government's amnesty offer.

"Most of the men — everyone here — is wanted by the regime," said Haj. "It's impossible for people here to go to regime areas."

Many male residents of Aleppo fear being taken in for their opposition activities or for mandatory military service.

Capitalizing on their push in battles over the past days, Assad's forces on Thursday took the Bani Zeid neighborhood on the northern edge of the Aleppo from the rebels as part of a steady advance meant to tighten the siege. State-run news agency SANA said the military has begun clearing land mines there and claimed dozens of gunmen laid down their weapons and surrendered in the neighborhood.

Assad's amnesty offer, which came in a presidential decree, included armed opposition fighters who surrender within three months and also urged all detainees to be freed. The decree, which was published by SANA, said that those who might set free their captives will be exempted from punishment if they turn themselves in within a month.

Assad has issued amnesty offers several times during Syria's civil war, now in its sixth year. The latest offer — like those before it — is largely seen by opposition fighters as a publicity stunt and psychological warfare against the rebels. More than a quarter of a million people have died and millions have been displaced since March 2011, when Syria's conflict erupted.

Separately, Shoigu also said that Moscow is sending a top general and experts to Geneva at the request of U.S. Secretary of State John Kerry to discuss the Aleppo crisis.

Shoigu said Putin, in response to a request by Kerry, ordered Gen. Stanislav Gadzhimagomedov and a group of experts to the Swiss city, which has hosted several rounds of Syrian talks and international negotiators trying to resolve the crisis.

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Issa reported from Beirut. Associated Press writers Sarah El Deeb in Beirut and Jamey Keaten in Geneva contributed to this report.