The Islamic State (Isis) militants destroyed an ancient 17th Century AD temple at the UNESCO world heritage site in Palmyra, Syria, activists and government officials said on Sunday.

The Syrian Observatory for Human Rights (SOHR), a monitoring group based in Britain, said in a statement that Isis terrorists planted "a large quantity of explosives" around the Temple of Baalshamin, to blow it up.

The 2000-year-old temple of Baalshamin was among the "most precious jewels" of Palmyra and had the most well-preserved structures in the ancient historical city of ruins. It was built in 17 AD and was expanded under the reign of Roman emperor Hadrian in 130 AD, according to The Guardian.

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According to SOHR, the temple is located "dozens of meters" away from the Palmyra Roman amphitheatre, where Isis held a mass execution, in which 25 Syrian soldiers were executed by teenaged- boys last month.

However, there are contradictory reports on when the structure was destroyed by Isis. While Maamoun Abdul-Karim, the head of Syria's Directorate of Antiquities and Museums, told Reuters that it was destroyed on Sunday (23 August), the SOHR has claimed that it was blown up by Isis last month.

"I am seeing Palmyra being destroyed in front of my eyes," Abdul-Karim told Reuters. "God help us in the days to come." 

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Since Isis took over the UNESCO heritage site in May, there have been concerns about the safety of the ancient city of ruins.

Last week, the Sunni terrorist group beheaded a noted Palmyra historian and archaeologist, Khaled Asaad, for helping Syrian officials to hide away precious artifacts from Palmyra.

The decapitated body of the 82-year old former head of Palmyra archaeological department was tied up and left on the street, with a board around him detailing his crimes of being a "traitor."

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