It comes just a week after the self-proclaimed Islamic State beheaded the Syrian archaeologist who looked after the ancient ruins.
IS has distributed five pictures showing the destruction of the Baal Shamin on social media.
They show explosives being carried inside, being set around the walls of the temple, the large explosion and then rubble.
Accompanying them is a caption that reads “The complete destruction of the pagan Baal Shamin temple”.
Newsagency AP says the images were placed on a social media site used by Islamic State militants, and are consistent with other AP reporting.
Syria’s director of antiquities has also confirmed that militants blew up the temple on Sunday, August 23.
UNESCO’s World Heritage Centre Director Koshore Rao has condemned the attack.
“There’s no words to describe it, you cannot sort of describe why it is happening. Obviously they are trying to erase the history and the identity of the people of Syria and erase all signs of idolatry which they feel conflicts with their belief system. UNESCO Director General Irina Bokova has also characterised this as cultural cleansing. These are acts that are terribly abhorrent and we condemn it with the strongest possible words.”
He says the destruction constitutes a war crime.
“The destruction of heritage monuments and religious sites constitutes, under the definition of the Rome statutes, as a war crime during both international conflict as well as national conflict”
The Baal Shamin temple was built nearly 2,000 years ago.
UNESCO described it as a symbol of Syria’s historical cultural diversity.
Historian Dan Cruickshank says the ruins at Palmyra are special.
“It is one of course, one of the great ruined classical cities from the ancient world. You travel from Damascus going east and you are in the desert and there’s an oasis in the distance and then suddenly you see a magical world and these great columns rising up and you know you are in the presence of something wonderful.”
He says the attacks are causing major cultural loss.
“These attacks are cultural terrorism, they are political. They are destroying memory, they are destroying architecture and they are destroying archaelogical sites in addition to destroying images. This is why these attacks are unprecedented. Where are these great locations on earth where the past somehow lives and you can to your imagination, go back and it is full of information. If we lose Palmyra, we are robbing generations yet born of a place of wonder and inspiration.”
UNESCO’s Koshore Rao agrees.
“The whole site sits at the crossroads of the trade routes between ancient Persia, China, India, in an oasis, and the architecture, the urban design that was developed there in those times has influenced later day architectural and urban design styles in the West. So. it is a masterpiece of human creative genius – if I may say so – that constitutes its outstanding universal value.”
Just last week, IS killed 82 year-old archaeologist Khaled al-Asaad, who had looked after the ancient ruins for four decades.
Prior to the group’s capture of Palmyra, Syrian officials said they’d moved hundreds of ancient statues and artefacts to safe locations, concerned the militants would destroy them.
The group seized the desert city in May from government forces but had initially left its ancient sites undamaged.
In June, it blew up two shrines that were not part of its Roman-era structures but which it regarded as sacrilegious.