What has just happened in Syria?

Syrian rebel forces have entered Damascus amid reports that President Bashar al-Assad has fled the country after 13 years of civil war.

Prime Minister Mohammed al-Jalali has said he is ready to support continuity of governance in the country.

It comes only 12 days after the Islamist militant group Hayat Tahrir al-Sham (HTS) and allied factions launched a major offensive in the north-west.

The rebels first captured the second city of Aleppo and then swept southwards down the highway to the capital as the Syrian military collapsed.

A peaceful, pro-democracy uprising against Assad in 2011 turned into a full-scale civil war that has devastated the country and drawn in regional and world powers.

More than half a million people have been killed and 12 million have been forced to flee their homes, about five million of whom are refugees or asylum seekers abroad.

Prior to the rebels' offensive, the war had felt as if it were effectively over after Assad's government regained control of most of Syria's cities with the help of Russia, Iran and Iranian-backed militias, and the front lines remained largely frozen.

However, large parts of the country were still out of the government's control.

These included northern and eastern areas controlled by a Kurdish-led alliance of armed groups supported by the United States, the Syrian Democratic Forces (SDF).

The rebels' last stronghold was in Aleppo and Idlib provinces, which border Turkey and where more than four million people were living, many of them displaced.

The enclave was dominated by HTS, but a number of allied rebel factions and jihadist groups were also based there. Turkish-backed rebel factions - known as the Syrian National Army (SNA) - also controlled territory there with the support of Turkish troops.

The Islamist militant group was set up in 2012 under a different name, al-Nusra Front, and pledged allegiance to al-Qaeda the following year.

Al-Nusra Front was regarded as one of the most effective and deadly of the groups ranged against President Assad. But its jihadist ideology appeared to be its driving force rather than revolutionary zeal - and it was seen at the time as at odds with the main rebel coalition known as the Free Syrian Army.

In 2016, Al-Nusra broke ties with al-Qaeda and took the name Hayat Tahrir al-Sham when it merged with other factions a year later.

However, the UN, US, UK and a number of other countries continue to consider HTS as an al-Qaeda affiliate and frequently refer to it as al-Nusra Front. The US has named the group's leader, Abu Mohammed al-Jawlani, as a specially designated global terrorist and offered a $10m reward for information that leads to his capture.

HTS consolidated its power in Idlib and Aleppo provinces by crushing its rivals, including al-Qaeda and Islamic State (IS) group cells. It set up the so-called Syrian Salvation Government to administer the territory according to Islamic law.

Jawlani said in a CNN interview on Friday that "the goal of the revolution remains the overthrow of this regime" and that he planned to create a government based on institutions and a "council chosen by the people".

For several years, Idlib remained a battleground as Syrian government forces tried to regain control.

But in 2020, Turkey and Russia brokered a ceasefire to halt a push by the government to retake Idlib. The ceasefire largely held despite sporadic fighting.

HTS and its allies said on 27 November that they had launched an offensive to "deter aggression", accusing the government and allied Iran-backed militias of escalating attacks on civilians in the north-west.

But it came at a time when the government had been weakened by years of war, sanctions and corruption, and its allies were preoccupied with other conflicts.

The Iran-backed Lebanese group Hezbollah, which was crucial in helping push back rebels in the early years of the war, had suffered recently from Israel's offensive in Lebanon. Israeli strikes had also eliminated Iranian military commanders in Syria and degraded supply lines to pro-government militias there. Russia had also been also distracted by the war in Ukraine.

Without them, Assad's forces were left exposed.

The HTS-led rebels took control of most of Aleppo - Syria's second largest city - on 30 November, only three days after launching their surprise offensive. They said they faced little resistance on the ground after the government rapidly withdrew its troops and security forces.

Assad vowed to "crush" the rebels with the help of his allies. Russian warplanes intensified their strikes on rebel-held areas and Iran-backed militias sent reinforcements to bolster the military's defensive lines around Hama - the next city south on the Aleppo-Damascus highway.

However, Hama fell to the rebels on Thursday after several days of fierce battles that eventually prompted the military to withdraw.

The rebels immediately declared that their next goal was to take Homs, Syria's third largest city, and achieved that on Saturday night after only a day of fighting.

At the same time, other rebel factions based in the south-west of the country, which borders Jordan, reached the suburbs of Damascus after taking control of the cities of Deraa and Suweida within only 24 hours.

Early on Sunday morning, the HTS-led rebels announced that they had entered Damascus and released detainees at the country's most notorious military prison, Saydanaya, where thousands of opposition supporters are believed to have been executed during the civil war.

Less than two hours later, they declared: "The tyrant Bashar al-Assad has fled."

"After 50 years of oppression under Baath rule, and 13 years of crimes and tyranny and [forced] displacement... we announce today the end of this dark period and the start of a new era for Syria," they said.

Senior army officers said the president flew out of the capital for an unknown destination shortly before the rebels arrived.

Assad's Prime Minister, Mohammed al-Jalali, then announced in a video that he was "ready to co-operate with" any leadership that was "chosen by the Syrian people".

Jawlani ordered his forces not to approach official institutions, saying they would remain under the authority of the prime minister until they were "officially" handed over.