Thousands of Syrian insurgents fanned out inside Aleppo in vehicles with improvised armor and pickups, deploying to landmarks such as the old citadel on Saturday, a day after they entered Syria's largest city facing little resistance from government troops, according to residents and fighters.

Witnesses said two airstrikes on the city's edge late Friday targeted insurgent reinforcements and hit near residential areas. A war monitor said 20 fighters were killed.

Syria's armed forces said in a statement Saturday that to absorb the large attack on Aleppo and save lives, it has redeployed and is preparing for a counterattack. The statement acknowledged that insurgents entered large parts of the city but said they have not established bases or checkpoints.

Insurgents were filmed outside police headquarters, in the city center, and outside the Aleppo Citadel. They tore down posters of Syrian President Bashar Assad, stepping on some and burning others.

The surprise takeover is a huge embarrassment for Assad, who managed to regain total control of the city in 2016, after expelling insurgents and thousands of civilians from its eastern neighborhoods following a grueling military campaign in which his forces were backed by Russia, Iran and its allied groups.

Aleppo has not been attacked by opposition forces since then. The 2016 battle for Aleppo was a turning point in the war between Syrian government forces and rebel fighters after 2011 protests against Assad's rule turned into an all-out war.

The push into Aleppo followed weeks of simmering low-level violence, including government attacks on opposition-held areas. Turkey, which has backed Syrian opposition groups, failed in its diplomatic efforts to prevent the Syrian government attacks, which were seen as a violation of a 2019 agreement sponsored by Russia, Turkey and Iran to freeze the line of the conflict.

The offensive came as Iran-linked groups, primarily Lebanon's Hezbollah, which has backed Syrian government forces since 2015, have been preoccupied with their own battles at home. A ceasefire in Hezbollah's two-month war with Israel took effect Wednesday, the day the Syrian opposition factions announced their offensive. Israel has also escalated its attacks against Hezbollah and Iran-linked targets in Syria during the last 70 days.

A witness in Aleppo said government troops remained in the city's airport and at a military academy but most of the forces have already filed out of the city from the south. Syrian Kurdish forces remained in two neighborhoods.

The redeployment "is a temporary measure and (the military central command and armed forces) will work to guarantee the security and peace of all our people in Aleppo," the military statement said.

Speaking from the heart of the city in Saadallah Aljabri square, opposition fighter Mohammad Al Abdo, said it was his first time back in Aleppo in 13 years, when his older brother was killed at the start of the war.

"God willing, the rest of Aleppo province will be liberated" from government forces, he said.

There was light traffic in the city center on Saturday. Opposition fighters fired in the air in celebration but there was no sign of clashes or government troops presence.

Abdulkafi Alhamdo, an teacher who fled Aleppo in 2016 and returned Friday night after hearing the insurgents were inside, described "mixed feelings of pain, sadness and old memories."

"As I entered Aleppo, I kept telling myself this is impossible! How did this happen?" He said he strolled through the city at night, visiting the citadel, where the insurgents raised their flags, a major square and the university of Aleppo, as well as the last spot he was in before he was forced to leave for the countryside.

"I walked in (the empty) streets of Aleppo, shouting, 'People, people of Aleppo. We are your sons,'" Alhamdo told The Associated Press in a series of messages.

The insurgents launched their shock offensive in the Aleppo and Idlib countryside on Wednesday and wrestled control of dozens of villages and towns before entering Aleppo on Friday.

The pro-government Al-Watan newspaper reported airstrikes on the edge of Aleppo city targeting rebel supply lines. It posted a video of a missile landing on a gathering of fighters and vehicles, in a street lined with trees and buildings.

Twenty fighters were killed in the airstrikes, said the Syrian Observatory for Human Rights. Aleppo residents reported clashes and gunfire. Some fled the fighting.

Schools and government offices were closed Saturday as most people stayed indoors, according to Sham FM radio, a pro-government station. Bakeries were open. Witnesses said the insurgents deployed security forces around the city to prevent any acts of violence or looting.

The U.N. Office for the Coordination of Humanitarian Affairs said the city's airport has been shut and all flights suspended. On Friday, Aleppo's two key public hospitals were reportedly full of patients while many private facilities closed, OCHA said.

In social media posts, the insurgents were pictured outside of Aleppo Citadel, the medieval palace in the old city center, and one of the largest in the world. In cellphone videos, they recorded themselves having conversations with residents they visited at home, seeking to reassure them they will cause no harm.

The Syrian Kurdish-led administration in the country's east said nearly 3,000 people, most of them students, had arrived in their areas after fleeing the fighting in Aleppo, which has a sizeable Kurdish population.

State media reported that a number of "terrorists," including sleeper cells, infiltrated parts of the city. Government troops chased them and arrested a number who posed for pictures near city landmarks, state media said.

On a state TV morning show Saturday, commentators said army reinforcements and Russia's assistance will repel the "terrorist groups," blaming Turkey for supporting the insurgents' push into Aleppo and Idlib provinces.

Russia's state news agency Tass quoted Oleg Ignasyuk, a Russian Defense Ministry official coordinating in Syria, as saying that Russian warplanes targeted and killed 200 militants who launched the offensive in the northwest on Friday. It provided no further details.