A leading Damascus cleric who fled Syria has been chosen at a meeting in Qatar to head a new coalition to oppose President Bashar al-Assad's government.
Cleric Moaz al-Khatib, former Sunni Muslim imam of the Umayyad mosque in Damascus, is seen as a moderate.
Earlier, Syrian opposition groups agreed a deal to bring together their disparate factions.
The fractious opposition has been under pressure from the US and other backers in the region to clinch a deal.
Sheikh Moaz al-Khatib, who is 52, left Damascus for Cairo in July after several periods of detention by the Syrian authorities.
As he signed the draft agreement that formed the opposition coalition with Syrian National Council head George Sabra, Mr al-Khatib called on the international community to "fulfil its pledges", the AFP news agency reported.
Last month he called for a political solution to save Syria from further destruction, arguing that negotiation would not "rescue the regime" but enable its departure with the least harm possible.
He had earlier attempted to bring the conflict to an end and in an interview with Reuters news agency in July said: "I want the Syrian people to remain as one hand."
More than 36,000 people have been killed in the long-running uprising against President Bashar al-Assad's government.
Many thousands more have fled the country since the unrest began last year.
Earlier on Saturday the Israeli military said it had fired warning shots into Syria, after a mortar round from Syria hit an Israeli outpost in the occupied Golan Heights.
It was the first time the two sides have exchanged fire since the 1973 Middle East war.
Ali Sadreddine al-Bayanouni, a Muslim Brotherhood delegate at the Qatar talks, said the new body would be called the National Coalition for Syrian Revolutionary and Opposition Forces.
The group, formed after a week of talks in Doha, will have two vice-presidents - prominent dissident Riad Seif and leading secular activist Suhair al-Atassi.
BBC Beirut correspondent Jim Muir described the coalition's leadership as a carefully balanced team that was set to become the face and voice of the Syrian opposition in the coming phase.
The Syrian National Council (SNC), which was formerly recognised as the main opposition, had been concerned it might be sidelined by the new opposition body.
One source at the meeting told Reuters that the SNC had agreed only under pressure and that it had been given a deadline of 10:00 (07:00 GMT) to sign up or risk being left out.
The new body had been proposed by Mr Seif with the backing of the US, which had signalled its frustration with the SNC.
"We signed an agreement to create [a] coalition of 60 members of the Syrian opposition," he said.
Delegates said the body would carry representation for ethnic Kurds, Christians, Alawites and women. Of the 60 places, 22 will be reserved for the SNC.
Bassem Said Ishak, of the SNC, said the Kurds required 48 hours to get the approval of their leadership.
The new body will also have a military council that will include the Free Syrian Army.
The BBC's Jim Muir, who was in Doha as the talks began last week, says the backers of the new body hope it will boost the mainstream of the Syrian opposition and sideline any extremist elements.
Turkish Foreign Minister Ahmet Davutoglu, who was in Doha for the culmination of the talks, said there was "no excuse now" for the international community not to recognise the Syrian opposition.
Violence continued inside Syria on Sunday.
Opposition activists said government forces had attacked an area along the border with Turkey, after rebels had captured a crossing point.
The activists said helicopters and artillery units had bombarded the Ras al-Ain border area.
Clashes were also reported in Damascus, Albu Kamal near the Iraqi border, Irbin and in Deir Ezzor in the east.
Meanwhile, the Israeli military said the shell from Syria that hit a military post in the Israeli-occupied Golan Heights was stray fire from fighting between Syrian government forces and rebels.
Israeli PM Benjamin Netanyahu warned Israel was "ready for any development" on the border with Syria.
Israel and Syria are still technically at war, and a UN force patrols the buffer zone.