Syrian regime jets have caused heavy damage to the country's greatest Crusader fort, Krak des Chevaliers, as the front line in the battle for the city of Homs moved to the world heritage site.
Opposition activists released video footage of the raid that showed a direct hit, a huge blast and the partial collapse of an internal tower. Other videos online showed at least one air strike on Saturday against the castle, which is on a hill near the city.
"This is the destruction caused by MiG air strike on the Krak des Chevaliers," an activist filming the damage can be heard saying.
The 12th-century rebel-held fortress is a target for the forces of President Bashar al-Assad as they wage an offensive to regain control of Homs, a strategic gateway to the north of the country.
Krak des Chevaliers, with the adjoining Qalat Salah el-Din fortress, is considered a crown jewel of the Middle East and one of the best-preserved Crusader castles in existence.
Built by the Knights Hospitallers, Krak des Chevaliers was described by Lawrence of Arabia as the "best preserved and most wholly admirable castle in the world".
Sited at the entrance to the Homs Gap, its value was crucial in crusades including the third when the English King Richard the Lionheart forced the Muslim leader, Saladin, into a treaty of peace.