A man rides a bicycle near damaged buildings in the rebel-held al-Sukkari neighborhood of Aleppo, Syria, on Oct. 19. (Abdalrhman Ismail/Reuters)

Russia and Syria, facing international allegations of war crimes, have begun a pause in airstrikes against eastern Aleppo that aid groups said would allow evacuation of about 200 severely wounded and sick people and delivery of food and medical supplies.

International aid officials said that they have asked for strikes in the rebel-held parts of the Syrian city to stop for at least five days but that Russia has so far agreed only to three. Although airstrikes began to diminish earlier this week, the pause officially began Thursday. U.N. humanitarian coordinator Jan Egeland said in Geneva that ambulances and aid-bearing trucks are expected to enter Aleppo on Friday.

The Russian Defense Ministry said President Vladi­mir Putin had personally ordered the respite. Kremlin spokesman Dmitry Peskov attributed what he described as a humanitarian gesture to “the political will of the Russian side.”

Russian and Syrian aircraft would refrain from bombing rebel-controlled eastern Aleppo, Peskov told reporters in Moscow, as long as “terrorists” inside the city did not use the time “for delivering strikes, for rearming and for building up their ammunition arsenals.”

U.N. officials described the pause as unilateral but said that rebel fighters, who have held eastern Aleppo for the past four years, had agreed to the humanitarian operations. Staffan de Mistura, the U.N. special envoy for Syria, said that the temporary halt to bombing was separate from sputtering international efforts to implement a Syria-wide cease-fire in the five-year civil war. He also said it was not part of his proposal to an estimated several hundred al-Qaeda-linked fighters and thousands of anti-government rebel fighters — the professed target of the Russian and Syrian airstrikes — to peacefully leave the city.

Drone footage shows the scale of destruction caused by airstrikes in the Syrian city of Aleppo, where fighting has intensified in recent weeks. (Reuters)

A cease-fire negotiated last spring between the United States and Russia, backing opposing sides of the conflict, lasted only a few weeks, after which Syrian troops, backed by Russian air power and artillery, closed off remaining rebel access routes to the city. A second truce effort last month fell apart in just a few days as Russia and Syria began a relentless bombing campaign against the now-surrounded eastern side of the city.

The ensuing carnage, while targeting hospitals, schools and other infrastructure and killing hundreds of civilians as escape routes were blocked, led the United States and much of the international community to accuse Russia and Syria of war crimes against the estimated 275,000 people remaining in eastern Aleppo.

The United Nations has repeatedly tried to negotiate among the parties on the ground — as well as their powerful supporters — to pause the fighting long enough to allow aid convoys to enter Aleppo and other besieged areas. While Russia and Syria have charged the rebels with numerous attacks, the opposition has no aircraft, and government forces surround a number of towns and cities. “The biggest obstacle and problem remains the government. Let’s be clear about this,” said one aid official who spoke on the condition of anonymity to avoid endangering chances for success this week.

Stephen R. O’Brien, the U.N. undersecretary general for humanitarian affairs, described constant, frustrating efforts to gain approval for a pause in fighting from government and opposition forces split into innumerable factions. If one side offers a pause, “then you have to wait for the other side to agree,” he said in an interview.

As in the current pause in Aleppo, convoy drivers — most of them local contractors — insist on waiting for at least “seven to nine hours to hear the guns fall silent, to give them the confidence to move toward conflict areas,” O’Brien said. But even with assurances, all involved are aware of the dangers.

“We’re not naive,” O’Brien said. “However brave they are, they’re not suicidal.”

Opposition groups “lost a lot of confidence” in government promises with the Sept. 19 bombing of a humanitarian convoy entering Aleppo during the last, brief truce, the aid official said. The United States, the United Nations and others have said Russian or Syrian aircraft carried out the attack, which killed at least 20 people. Russia has denied involvement and suggested that an armed U.S. drone was in the area, which the United States has denied.

The plan for Friday, the aid official said, is for a convoy of ambulances to first enter eastern Aleppo, followed by trucks carrying food and medical aid. Some of the supplies will travel by road about 35 miles from the Turkish border, while others will cross from the government-held western part of the city. “We would do it in one day and out,” the official said. “The trucks are ready to roll.”

The convoys are to be accompanied by U.N. officials, including about 10 international staffers, and Jordanian Ali Zaatari, the Damascus-based head of U.N. operations in Syria.

Russia did not link the promised pause to anything other than assurances that opposition forces not use the time to rearm. The Russian and Syrian governments have urged residents of the city to evacuate and promised them safe passage.

In an interview with Swiss television this week, Syrian President Bashar al-Assad said that the civilians wanted to leave but were being prevented by the rebels. De Mistura, the U.N. special envoy, disagreed, saying that “from what I hear . . . the people do not want to leave their places, they do not want to become refugees. They want to stay in their place, but they do request, stop the bombing, which needs to be, by the way, from both sides.”

Abdulrahman Marea, 30, lives in a neighborhood in eastern Aleppo. “We don’t trust the regime at all,” Marea said via the WhatsApp messenger service. “. . . We’re even hearing some gunfire in areas where these [protected exit] corridors are supposed to be, so of course we don’t trust the regime’s promise of helping people leave the city.”

The Syrian military used loudspeakers Thursday to press a similar message on opposition fighters. The Associated Press reported one repeated message that blared: “The battle for returning Aleppo to the nation’s fold is in its last phases. There is no point in continuing the fight.”

“We don’t trust them,” said Abu al-Hasan, a commander of the Fastaqim rebel unit in Aleppo, referring to Russia and the Syrian government. “They always talk about cease-fires and truces, but what they do is constantly target civilians and violate the laws of war.”

Opposition fighters and residents in the city’s east fear that such a lull in fighting and the offer of safe escape is just part of a long-running policy by Assad’s government, implemented in other areas, of forcing opposition areas to “surrender or starve.”

North of the city, meanwhile, Turkey carried out air raids overnight against Kurdish forces. The attacks targeted positions of the People’s Protection Units, or YPG, a force that has allied with the United States to fight Islamic State forces in northeastern Syria.

Military officials told Turkey’s Anadolu news agency that the air raids struck 18 targets, killing as many as 200 Kurdish fighters.

In August, Turkish troops advanced inside northern Syria, supposedly as part of an assault against Islamic State militants, but many say it was actually designed to prevent Kurdish militants in Syria from securing more territory along the border with Turkey.

Syria’s Kurds are trying to carve out an autonomous region in that area, a move that Turkey fears could embolden its own Kurdish separatists.

Hugh Naylor in Beirut, Zakaria Zakaria in Istanbul and Brian Murphy in Washington contributed to this report.