DAMASCUS — Thousands of Syrians gathered Friday in Damascus' historic main mosque for the first Muslim Friday prayers since the downfall of former President Bashar Assad, while giant crowds celebrated in the capital's largest square.

The gatherings were a major symbolic moment for the dramatic change of power in Syria, nearly a week after insurgents swept into Damascus, ousting the Assad-led state that had ruled the country for a half century with an iron grip. It came as U.S. Secretary of State Antony Blinken met with allies around the region looking to shape the transition, calling for an "inclusive and non-sectarian" interim government.

After talks in Jordan and Turkey — which backs some of the insurgent factions — Blinken arrived in Iraq on a previously unannounced stop. So far, U.S. officials have not talked of direct meetings with Syria's new rulers.

The main insurgent force, Hayat Tahrir al-Sham, has been working to establish security and start a political transition after seizing the capital early Sunday. At the same time, they have tried to reassure a public that is both stunned by Assad's fall and concerned over extremist jihadis among the rebel ranks. The insurgents' leadership says it has broken with its extremist past, though HTS is still labeled a terrorist group by the United States and European countries.

The group's leader, Ahmad al-Sharaa, formerly known as Abu Mohammed al-Golani, appeared in a video message Friday congratulating "the great Syrian people for the victory of the blessed revolution."

"I invite them to head to the squares to show their happiness without shooting bullets and scaring people," he said. "And then after we will work to build this country and as I said in the beginning, we will be victorious by the help of God."

Syrians celebrate in the historic heart of Damascus

Huge crowds, including some insurgent fighters, packed Damascus' historic Umayyad Mosque in the capital's old city for Friday prayers, many of them waving the rebel opposition flag — with its three red stars — which has swiftly replaced the Assad-era flag with with its two green stars. According to Arab TV stations, the Friday sermon was delivered by Mohammed al-Bashir, the interim prime minister installed by HTS this week.

The scene resonated on multiple levels. The mosque, one of the world's oldest dating back some 1,200 years, is a beloved symbol of Syria, and sermons there like all mosque sermons across Syria had been tightly controlled under Assad's rule. Also, in the early days of the anti-government uprising in 2011, protesters would often emerge from Friday prayers to march in rallies against Assad — before he launched a brutal crackdown that turned the uprising into a long and bloody civil war.

"I didn't step foot in Umayyad Mosque since 2011," because of the tight security controls around it, said one worshipper, Ibrahim al-Araby. "Since 11 or 12 years, I haven't been this happy."

Another worshipper, Khair Taha, said there was "fear and trepidation for what's to come — but there is also a lot of hope that now we have a say and we can try to build."

Blocks away in Damascus' biggest roundabout, named Umayyad Square, thousands gathered, including many families with small children — a sign of how, so far at least, the country's transformation has not seen violent instability.

"Unified Syria to build Syria," the crowd chanted. Some shouted slurs against Assad and his late father, calling them pigs, an insult that would have previously led to offenders being hauled off to one of the feared detention centers of Assad's security forces.

One man in the crowd, 51-year-old Khaled Abu Chahine, was originally from the southern province of Daraa, where the 2011 uprising first erupted. He said he hoped for "freedom and coexistence between all Syrians, Alawites, Sunnis, Shiites and Druze. No to racism."

"The former government was a government of crime and executions," he said, calling on foreign nations "hosting these gangs to bring them to justice and those who are in Syria and committed crimes should face justice."

The interim prime minister, al-Bashir, had been the head of a de facto administration created by HTS in Idlib, the opposition's enclave in northwest Syria. The rebels had been bottled up in Idlib for years before fighters broke out in a shock offensive and marched across Syria in 10 days. They finally seized Damascus early Sunday, as Assad's military and security forces melted away.

Among the crowd in Umayyad Square, Wardan Aoun — who identified himself as a fighter from Idlib — praised the new administration. ""There is a good government now ... We lived in Idlib under this government and there is no corruption there."

U.S. and its allies try to shape a rapidly changing Syria

Al-Sharaa, HTS' leader, has promised to bring a pluralistic government to Syria, seeking to dispel fears among many Syrians — especially its many minority communities — that the insurgents will bring a hardline, extremist rule.

Another key factor will be winning international recognition for a new government in Syria, a country where multiple foreign powers have their hands in the mix.

Turkey controls a strip of Syrian territory along the shared border and backs an insurgent faction uneasily allied to HTS — and is deeply opposed to any gains by Syria's Kurds. The U.S. has troops in eastern Syria to combat remnants of the Islamic State group and backs Kurdish-backed fighters who rule most of the east. Since Assad's fall, Israel has bombed sites all over Syria, saying it is trying to prevent weapons from falling into extremist hands, and has seized a swath of southern Syria along the border with the Israeli-occupied Golan Heights, calling it a buffer zone.

After talks with Turkey's Foreign Minister Hakan Fidan, Blinken said there was "broad agreement" between Turkey and the United States on what they would like to see in Syria.

That starts with an "interim government in Syria, one that is inclusive and non-sectarian and one that protects the rights of minorities and women" and does not "pose any kind of threat to any of Syria's neighbors," Blinken said.

Fidan said the priority was "establishing stability in Syria as soon as possible, preventing terrorism from gaining ground, and ensuring that IS and the PKK aren't dominant" — referring to the Islamic State group and the Kurdistan Workers Party. Turkey considers the PKK a terrorist group — as it does the Kurdish-backed forces in Syria backed by the United States.

In Baghdad, Blinken met with Iraqi Prime Minister Mohammed al-Sudani, saying both countries wanted to ensure the Islamic State group — also known by its Arabic acronym Daesh — doesn't exploit Syria's transition to re-emerge.

"Having put Daesh back in its box, we can't let it out, and we're determined to make sure that that doesn't happen," Blinken said.