They said al-Qaida's affiliate in Syria carried out the destruction. It showed the determination of extremists to drive Shiites out of the village of Hatla in the Deir el-Zour region near Iraq. Last week rebels battled pro-regime militiamen there, killing more than 60 Shiite fighters and civilians, according to activists.
In Lebanon, gunmen deployed in the streets of the northeast and set up roadblocks in protest following the killing of four Lebanese Shiite men in an ambush, security officials said today.
They said the men were from the powerful Jaafar and Amhaz clans, triggering fears of retaliation.
It was not immediately clear how they were killed or what the motive was, but today's ambush is believed to be related to sectarian tensions related to the Syrian civil war.
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Tensions between Sunnis and Shiites in Lebanon increased after the Shiite Iranian-backed Hezbollah openly joined the fight in Syria on the side of President Bashar Assad.
In amateur videos of the mosque destruction in Syria, fighters walked into the mosque in Hatla and trampled on books, some with covers showing pictures of Shiite clerics. The videos then showed an explosion that brought down the building.
Today's video posted on the Internet appeared genuine and corresponded with other Associated Press reporting from the area.
Rami Abdul-Rahman, director of the Britain-based Syrian Observatory for Human Rights, said that the mosque was demolished on Friday, three days after the battle. Other videos that emerged earlier have showed rebels cursing Shiites and suggested fighters had burned Shiite homes.
The town is home to several thousand people, about 30 per cent of them Shiites. It was considered a pro-regime community in the Euphrates River valley, where rebels, including the al-Qaida-linked group Jabhat el-Nusra, have taken over much of the surrounding territory.