Pictures show the once famous landmark reduced to a pile of rubbleThe minaret of one of Syria's most famous mosques has been destroyed during clashes in the northern city of Aleppo.
The state news agency Sana accused rebels of blowing up the 11th-Century minaret of the Umayyad Mosque.
However, activists say the minaret was hit by Syrian army tank fire.
The mosque, which is a Unesco world heritage site, has been in rebel hands since earlier this year but the area around it is still contested.
Last October Unesco appealed for the protection of the site, which it described as "one of the most beautiful mosques in the Muslim world".
Images posted on the internet showed the minaret reduced to a pile of rubble in the mosque's tiled courtyard.
Aleppo's Umayyad Mosque
- The Great Mosque, at the heart of the Old City of Aleppo, was founded by the Umayyad dynasty in 715 on the site of a Byzantine church
- The mosque had to be rebuilt after being damaged by a fire in 1159, and again following the Mongol invasion in 1260
- The oldest surviving part was the 45m (148ft) minaret, which dated back to 1090
- Unesco describes the world-heritage-listed mosque as one of the most beautiful in the Muslim world
- The mosque was badly damaged by fire during heavy fighting in the Old City in October 2012
Other parts of the mosque complex - which dates mostly from the 12th Century - have been badly damaged by gunfire and shell hits.
A report by Sana said fighters from the al-Qaeda-linked Jabhat al-Nusra group had destroyed the once famous landmark.
It quoted an official source saying that "terrorists... placed explosive materials in the minaret and the mosque's southern door and set them off".
However, Aleppo-based activist Mohammed al-Khatib, quoted by AP news agency, said a tank shell had "totally destroyed" the 45m (148ft) minaret.
The mosque has suffered extensive damage during months of fighting, with antique furnishings and intricately sculpted colonnades affected.
Reports say some ancient artefacts have also been looted, including a box purported to contain a strand of the Prophet Muhammad's hair.
However, rebels said they had salvaged ancient handwritten Koranic manuscripts and hidden them.
Footage uploaded on YouTube purports to show Aleppo minaret no longer exists
Earlier, rebels and government forces reportedly clashed near Aleppo as they fought for control of a military airbase.
Rebels took a key military position outside the Minnigh airport on Tuesday and launched another raid on Wednesday, according to opposition activists with the Syrian Observatory for Human Rights.
"The rebels, who have laid siege to the airport for months now, entered it for the first time around dawn," Rami Abdel Rahman, director of the UK-based activist group, told AFP news agency.
Heavy fighting was taking place in the grounds, he added.
Analysts say losing control of the airport would be a strategic blow for the government.
The Free Syrian Army has been trying to seize a number of airbases in the area to disrupt regime supply routes.
In another development on Wednesday, Syria's Deputy Foreign Minister told the BBC that his country was fighting a war against terrorism.
Faisal Mekdad said the international community should be supporting President Assad and his government.
Asked if he thought the Syrian government could still defeat the rebels, he said: "We shall defend our sovereignty and independence to the last drop. We have a strong army, we have a lot of our people who are supporting the government, who are uniting their ranks to defend the country. And in such a situation they will never defeat Syria."
According to the UN, at least 70,000 people have been killed in the civil war and more than a million are now living as refugees in neighbouring countries.