BEIRUT (Reuters) - Sunni Muslim insurgents have killed about 60 Shi'ite Muslims in a rebel-held eastern Syrian town where President Bashar al-Assad's agents had been trying to recruit and arm fighters for his cause, according to opposition sources on Wednesday.
The attack was another sign of how a revolt that began more than two years ago with peaceful protests against four decades of Assad family rule is descending into sectarian bloodshed.
A video posted online by rebels on Tuesday, entitled "The storming and cleansing of Hatla" showed dozens of gunmen carrying black Islamist flags celebrating and firing guns in the streets of a small town as smoke curled above several buildings.
"We have raised the banner 'There is no God but God' above the houses of the apostate rejectionists, the Shi'ites, and the holy warriors are celebrating," the voice of the cameraman says.
Many of the fighters involved in the attack were said to be from the al Qaeda-linked Nusra Front. Hardline Sunni groups often refer to Shi'ites as rejectionists because they deny the legitimacy of the Prophet Mohammad's first successors.
"This is a Sunni area, it does not belong to other groups," one fighter shouted in the video purportedly filmed in the town of Hatla in the eastern province of Deir al-Zor.
The Syrian Observatory for Human Rights, a pro-opposition monitoring group that has reported abuses on both sides of the conflict, put the death toll in Tuesday's attack at 60, saying most victims were pro-Assad Shi'ite militiamen. Assad's minority Alawite sect is rooted in Shi'ite Islam. Most rebels are Sunnis.
The Observatory said many Shi'ite civilians, a minority in the mixed town of Hatla, had fled elsewhere in the province.
Some opposition activists said the attack included summary killings and the burning of Shi'ite places of worship.
Activist Karam Badran, who spoke to Reuters from Deir al-Zor, said only 20 people had been confirmed killed in Hatla but that another 20 had been taken hostage by the rebels.
He said the main motive for the violence was not sectarian, but what he and the Observatory said were recent government attempts to recruit militiamen of all faiths in an area held by rebels for a year, without any harm coming to Shi'ites there before.
Badran said the Hatla killings had also followed an attack on Monday by pro-Assad militiamen on a rebel checkpoint outside the provincial capital Deir al-Zor, in which several opposition fighters had been killed and dozens wounded.
"Three of the men killed were three Shi'ite clerics. They were executed and hung on the gates of the town," Badran said. "But among the dead were also Sunnis (who had joined pro-Assad militia). This is really about betrayal."
(Reporting by Erika Solomon; Editing by Alistair Lyon)