Forces loyal to Syria's President Bashar al-Assad patrol at Tal-al-Zrazir neighbourhood in Aleppo city
Hundreds of shops were burning in the ancient covered market in Aleppo on Saturday as fighting between rebels and state forces in Syria's largest city threatened to destroy a UNESCO world heritage site.
The uprising-turned-civil war that is now raging across Syria has killed more than 30,000 people, according to activist groups such as the Syrian Observatory for Human Rights, reports Reuters.
But beyond the dramatic human cost, many of Syria's historic treasures have also fallen victim to an 18-month-old conflict that has reduced parts of some cities to ruins.
Rebels fighting to topple President Bashar al-Assad announced a new offensive in Aleppo, Syria's commercial hub of 2.5 million people, on Thursday, but neither side has appeared to make significant gains.
In Aleppo, activists speaking via Skype said army snipers were making it difficult to approach the Souk al-Madina, the medieval market of vaulted stone alleyways and carved wooden facades in the Old City, once a major tourist attraction.
Videos uploaded to YouTube showed dark black clouds hanging over the city skyline.
Activists said the fire might have been started by shelling and gunfire on Friday and estimated that between 700 and 1,000 shops had been destroyed so far. The accounts were difficult to verify because of government restricts on foreign media.
Aleppo's Old City is one of several locations in Syria declared world heritage sites by UNESCO, the United Nations cultural agency, that are now at risk from the fighting.
UNESCO believes five of Syria's six heritage sites - which also include the ancient desert city of Palmyra, the Crac des Chevaliers crusader fortress and parts of old Damascus - have been affected.
The British-based Observatory for Human Rights, which has a network of activists across Syria, said Assad's forces and rebels blamed each other for the blaze.
Heavy clashes erupted outside several military sites in Aleppo on Saturday evening. Activists said rebels were battling government forces outside the Neirab military air base.
The Observatory said clashes outside a base used for artillery training had set a nearby building alight and killed three people.
Fighting was also reported outside Bab Antakya, a stone gateway to Aleppo's Old City, which sits on ancient trade routes and survived a parade of rulers throughout its construction between the 12th and 17th century.
Rebels said they had taken the gate, but some activists said the fighting continued and neither side was truly in control.