Syrian President Bashar al-Assad has fled the country after a stunning offensive by rebels who seized the capital city of Damascus and toppled the dynasty that had ruled for 50 years.

Amid scenes of jubilation on Sunday, the rebels proclaimed “the city of Damascus is free from the tyrant Bashar al-Assad” and “Assad has fled” after various factions encircled the capital.

Russia, a longtime backer of the Assad regime, said the Syrian president had resigned, left the country and ordered a peaceful transition of power. Russian state newswire Tass later said he and his family had arrived in Moscow where they had been offered asylum.

“The future is ours,” said Abu Mohammad al-Jolani, leader of the triumphant Hayat Tahrir al-Sham Islamist group, in a statement read out on Syrian state television.

HTS, once an affiliate of al-Qaeda, led disparate rebel factions in a lightning 12-day offensive that brought the Assad dynasty to an ignominious end and has shaken the region.

Last week the group seized Aleppo, Syria’s second city, within 48 hours before quickly marching south towards the capital.

Israeli Prime Minister Benjamin Netanyahu hailed a “historic day in the annals of the Middle East” but sent tanks and infantry into a demilitarised buffer zone on the Syrian side of the Golan Heights.

Netanyahu said a 1974 ceasefire agreement had “collapsed” after Syrian army units abandoned their positions and Israeli forces needed “to ensure no hostile force embeds itself right next to the border of Israel”.

US president-elect Donald Trump wrote in a social media post: “Russia, led by Vladimir Putin, was not interested in protecting [Assad] any longer.”

He added: “Russia and Iran are in a weakened state right now, one because of Ukraine and a bad economy, the other because of Israel and its fighting success.”

US President Joe Biden said Washington would “engage with all Syrian groups”, reflecting how it aims to influence what he described as “the best opportunity in generations for Syrians to forge their own future”.

Biden said the US would seek to ensure Isis could not take advantage of the situation, adding the American military had launched dozens of air strikes on Sunday targeting camps and operatives of the Jihadist group in Syria.

In Damascus, rebel factions were already attempting to enforce law and order, imposing a curfew, warning of legal penalties for theft and errant gunfire, taking over ministries and installing police officers amid widespread looting.

The Financial Times was referred to a new Ministry of Communications building, where rebel officials had set up shop, when inquiring about media access to the city after curfew.

Signalling his efforts to secure an orderly transition, Jolani declared that Syrian state institutions would remain under the supervision of the Assad-appointed prime minister until a handover.

Near the city’s Umayyad square, the streets were littered with thousands of bullet casings — remnants of celebratory gunfire. The sound of artillery shelling and sporadic gunfire could still be heard in central Damascus on Sunday evening.

“I can’t believe it. Everyone is in the street, everyone is shouting,” said Abdallah, a Damascus resident. “It’s something historical. No one has suffered as much as the Syrian people.”

Videos sent to the Financial Times by a Damascus resident showed people inside the presidential palace, rummaging through rooms and smashing pictures of the Assad family.

A man dressed in civilian clothing appeared on Syrian state TV on Sunday morning declaring that the rebels had “liberated” Damascus and released detainees from “regime prisons”.

But while the news sparked celebrations across Syria, it also ushers in a period of huge uncertainty for a nation shattered and fragmented after 13 years of civil war, and for the wider region.

The country borders Turkey, Israel, Jordan, Iraq and Lebanon, with HTS working with Turkish-backed rebels operating under the umbrella of the Syrian National Army.

However, Syria is home to myriad factions and the degree of co-ordination between them all is unclear.

Turkey’s foreign minister Hakan Fidan hailed the end of the Assad regime, but also warned that Ankara was concerned “Isis and other terrorist organisations . . . will take advantage of this process”.

An Arab diplomat said regional powers, including Saudi Arabia, Iran, Iraq, Turkey, Jordan, Russia and Qatar had agreed to co-ordinate efforts to stabilise the situation.

Syrian Prime Minister Mohammad Ghazi al-Jalali said he was ready to work with any leadership chosen by the people and called for unity.

“We are ready to co-operate and all the properties of the people and the institutions of the Syrian state must be preserved,” he added.

Multiple explosions were heard in Damascus on Sunday afternoon. At least some of the strikes — whose origins were unknown — hit the Syrian security complex.

Assad, a London-trained eye doctor, had ruled Syria since 2000, when he succeeded his late father Hafez al-Assad.

Civil war broke out in 2011 after his forces brutally suppressed a popular uprising.

He managed to cling to power with the backing of Iran and Russia, which provided vital air power, and in recent years his regime had regained control over most of the country.

However, he presided over a hollowed-out, bankrupt state — and even many among his own Alawite community appeared to have given up on the regime after years of conflict and economic hardship.

When HTS mounted its offensive on November 27, regime forces seemed to melt away, while Russia, Iran and Hizbollah, the Lebanese militant group, were all distracted by their own conflicts.

The rebels’ success is a humiliating blow to Iran, whose support for Assad had given it a “land bridge” across Syria to Lebanon and its proxy Hizbollah.

Iran’s foreign ministry on Sunday urged respect for Syria’s “territorial integrity” and called for “an immediate end to military conflicts” in the Arab state.

Assad’s exit is also a setback for Russia, which gained access to air and naval bases on the Mediterranean after intervening in the war in 2015.

Russia said on Sunday its military bases in Syria were “on high alert”. Moscow spoke of “no serious threat to their security”, but Russian military bloggers said it was preparing to evacuate its Khmeimim air base and naval site in Tartus.

John Foreman, a former UK defence attaché in Moscow, said the bases’ loss would be “a major strategic reversal” for Russia and without them it would be “harder for the Russian navy to maintain an enduring maritime presence in the Mediterranean or Red Sea to challenge Nato”.

Additional reporting by Max Seddon in Berlin, John Paul Rathbone in London, Neri Zilber in Tel Aviv, Felicia Schwartz in Washington

Cartography by Steven Bernard