Syrian opposition forces have entered Aleppo just three days into their surprise offensive, marking the first time they have set foot in the country’s second-largest city since government forces recaptured the city in 2016.

The rebels launched a surprise attack this week, sweeping eastward through several villages outside the city and reigniting a conflict that had been largely static for years.

By Friday evening, opposition forces had reached the city center, according to footage verified by CNN, which showed camo-clad fighters waving the flag of the Syrian opposition in a central square.

The offensive, which began Wednesday, is the first major flare-up in years between the Syrian opposition and the regime of President Bashar al-Assad, who has ruled the war-torn country since 2000.

The official Syrian military said it was confronting a “major attack” and claimed it is “reinforcing all locations along the various battlefronts,” but multiple residents of the city say regime forces have pulled back from several neighborhoods in the western part of Aleppo.

On Friday, the newly formed armed opposition coalition, the Military Operations Command, said it seized control of the Syrian government’s Military Scientific Research Center on the outskirts of Aleppo city after “intense clashes with the regime forces and Iranian militias.” It later shared a video of Syrian regime tanks leaving Aleppo as rebel forces advanced.

The armed opposition forces continued to edge further into the city throughout Friday afternoon. In a video geolocated by CNN, fighters were seen by the statue of Bassel al-Assad, the deceased brother of President Assad, on the eastern edge of the city’s New Aleppo district. One fighter was seen lowering a Syrian flag from its mast.

A fluid situation

The situation in Aleppo remained fluid as the day progressed, as armed opposition forces appeared to continue their rapid advance.

Two videos captured in the central Saadallah al-Jabiri Square show camo-clad fighters waving the flag of the Syrian opposition and yelling “Allahu Akbar”—meaning “God is great” in Arabic—in the nearly deserted plaza.

The armed rebels also appeared at Aleppo’s historic citadel, verified footage shows, nearly a mile (1.59km) to the southeast, verified footage shows.

Pro-Syrian government social media channels have disputed the extent of the opposition’s advance. Two videos posted on pro-government Telegram channels, purportedly show empty squares in northwest Aleppo, as men claim that there are no rebels in that part of the city.

In an attack earlier Friday, an artillery shell struck Aleppo University’s student housing, killing four people, according to Syria’s state news agency, SANA, which blamed opposition factions for the attack. The spokesperson for the rebel groups Hassan Abdulghani refuted the accusations by the Syrian government media as “baseless lies.”

An Aleppo University employee, speaking anonymously for security reasons, confirmed that an artillery shell hit the second floor of a dormitory with students inside at the time. A video circulating on social media, geolocated by CNN, shows young men running out of a dormitory in Aleppo University campus and carrying an injured individual.

On Thursday, at least 15 civilians, including six children and two women, were killed, and 36 others were injured in airstrikes and shelling on rebel-held areas in Aleppo and Idlib countryside, according to the White Helmets, a volunteer rescue group. Iranian state media said that an Islamic Revolutionary Guards Corps (IRGC) Brigadier General Kioumars Pourhashemi was also killed in the city.

In a call with his Syrian counterpart to discuss the escalation, Iran’s foreign minister Abbas Araghchi accused the United States and Israel of the “reactivation” of the rebels, and “stressed the continued support” of Iran to the Syrian government and army.

The Syrian government responded with airstrikes on the city of Idlib, one of the last remaining rebel strongholds and home to more than 4 million people. The White Helmets said “Russian-Syrian alliance aircraft” had struck “residential neighborhoods, a gas station and a school in Idlib city” on Friday, killing at least four people and injuring six others.

Videos geolocated by CNN showed damage at a gas station in Idlib. In one video, a man wearing a press jacket films himself as he runs through a burning gas station after an airstrike. He takes the hand of a screaming child, with blood running down his face.

“I want my dad, I want my dad. He’s burned, he’s in the fire,” the boy says, as he is led out of the gas station by the journalist.

The Russian air force on Friday launched an aerial offensive against Syrian armed opposition forces in Aleppo and Idlib provinces, according to Russian state media TASS. Russia claimed to have killed at least 200 members of Hay’at Tahrir al-Sham (HTS), a Syrian jihadist group that went by the name Al-Nusra Front when they were affiliated with Al Qaeda.

“Providing support to the Syrian Arab Army, the Russian Aerospace Forces are carrying out missile and bomb strikes on the equipment and manpower of illegal armed groups, command posts, warehouses, and artillery positions of terrorists,” TASS reported, adding that Russian operations continue.

Earlier on Friday, the Kremlin’s spokesman Dmitry Peskov called on the Syrian authorities to “quickly restore order in this area and restore constitutional order.” Both Iran and Russia are key allies to Syria.

Syria’s civil war began during the 2011 Arab Spring as the regime suppressed a pro-democracy uprising against Assad. The country plunged into a full-scale civil war as a rebel force was formed, known as the Free Syrian Army, to combat government troops.

The conflict swelled as other regional actors and world powers – from Saudi Arabia, Iran, the United States to Russia – piled in, escalating the civil war into what some observers described as a “proxy war.” ISIS was also able to gain a foothold in the country before suffering significant blows.

Since the 2020 ceasefire agreement, the conflict has remained largely dormant, with low-level clashes between the rebels and Assad’s regime.

More than 300,000 civilians have been killed in more than a decade of war, according to the United Nations, and millions of people have been displaced across the region.