BEIRUT, March 26 (Reuters) - Islamist fighters from an al Qaeda splinter group bombed a large Shi'ite Muslim shrine in the eastern Syrian city of Raqqa on Wednesday, activists said.
The mosque of Ammar bin Yassir and Oweis al-Qarni was once a destination for Shi'ite Muslim pilgrims from Iran, Lebanon and Iraq before it was taken over a year ago by Sunni rebels battling to overthrow President Bashar al-Assad.
One photo posted on Twitter on Wednesday under the heading "the pagan Iranian shrine" showed extensive damage to the exterior walls and roof of the site, a turquoise and white complex of domes and minarets centred around a tiled courtyard.
Another picture showed concrete and twisted metal strewn on the street outside the mosque - built under Assad's rule with support from Shi'ite Iran - while another showed an interior wall that had collapsed inward.
The Syrian Observatory for Human Rights monitoring group said the al Qaeda splinter group Islamic State in Iraq and the Levant (ISIL) had set off two powerful explosions at the mosque early on Wednesday.
Many fighters from ISIL and other radical Sunni Islamist groups in Syria deem Shi'ites as infidels and consider their shrines idolatrous, and therefore legitimate targets.
Their attacks have stirred fears in neighbouring Turkey that the Islamists' next target will be the tomb of Suleyman Shah, grandfather of the Ottoman Empire, which lies on the Euphrates river inside Syria but is guarded by Turkish special forces.
Ankara regards the tomb as sovereign Turkish territory under a treaty signed with France in 1921, when Syria was under French rule, and threatened earlier this month to retaliate for any attack on the mausoleum.
President Abdullah Gul said on Sunday Turkey would defend the site in the same way it would defend any Turkish land. "However the motherland is protected, that place will be protected in the same way," he said. (Reporting By Dominic Evans; Editing by Janet Lawrence)