President Bashar al-Assad's forces destroyed the minaret of the historic Omari mosque where Syria's uprising erupted two years ago in the southern city of Daraa, opposition activists said on Sunday.
In amateur video footage the activists uploaded to YouTube, the mosque can be seen at the end of a street, its towering minaret toppling over after apparent shelling and crumbling into rubble and dust.
Other videos posted online show the mosque, which is thought to date back to the 7th century, had been targeted in shelling for several days.
"This regime of unrestrained barbarism targeted with tanks the minaret of the Omari mosque, a place full of symbols of civilisation and spirituality and humanity," said the opposition Syrian National Council.
"The minaret of this mosque, which was build by Caliph Omar bin al-Khattab, is the first in the whole of the Levant, and has been destroyed by the soldiers of the tyrant," it added, referring to President Assad.
The Council noted the mosque had played a pivotal role in the beginning of the uprising against Assad, which sprung in large part from the city of Daraa after the arrest and torture of two boys.
"It was the first place that embraced the Syrian revolution during its infancy, the first wave of demonstrations of pride and dignity came out through its doors," said the Council.
"The first martyrs fell on its walls and the first wounded were treated on its floors."
The Local Coordination Committees activist network condemned the destruction of the minaret as a "barbaric act... which adds a new crime to the list of Assad's crimes".
"It is not just stones that are destroyed but also religious and historic heritage cherished by the Syrian people," said the LCC.
As Syria's conflict continues into a third year, an increasing number of the country's key heritage sites, both religious and cultural, are being damaged in the fighting.
International authorities including UNESCO have expressed concern that numerous sites in the country, including some classified as World Heritage sites, are being seriously damaged.
Syria has six sites inscribed on the UNESCO World Heritage list, including the old cities of Damascus and second city Aleppo, and the famed Crac des Chevaliers crusader castle.
The Al-Assad regime troops destroy the minaret of a mosque, which was built by Caliph Omar bin al-Khattab; the first in the whole of the Levant