The Islamic State (IS) jihadist group has planted explosives in the ruins of the central Syrian city of Palmyra, a monitoring group claimed Sunday.

The Syrian Observatory for Human Rights said the Islamic State militants have planted mines and explosives in the ruins of city, according to BBC News. Palmyra is home of world famous 2,000-year-old ruins, which UNESCO has designated a World heritage site.

However, the U.K.-based monitoring group said it was not clear whether the jihadists were going to blow up the ancient sites or use the explosives to prevent government forces from advancing into Palmyra. The extremist outfit seized the central Syrian city in May and blew up a notorious military prison in the city shortly after.

"They have planted it yesterday. They also planted some around the Roman theater [pictured above], we still do not know the real reason," said Rami Abdel Rahman, director of group, DW reported. The activist group depends on sources inside Syria for its information.

"We have preliminary information from residents saying that this is correct, they have laid mines at the temple site. I hope that these reports are not correct, but we are worried," he added, according to Agence France Presse.

Syrian regime forces have already launched counter-offensives to recapture the ancient town. "The regime forces are to the west outside the city, and in recent days they have brought in reinforcements suggesting they may be planning an operation to retake Palmyra," Rahman said.

Syria's head of antiquities Maamoun Abdulkarim confirmed the report of Islamic State planting bombs in Palmyra. "The city is a hostage in their hands, the situation is dangerous," Abdulkarim said, Reuters reported.