The U.N. cultural agency's chief says she is alarmed by developments in Syria, where Islamic State militants are getting closer to the ancient city of Palmyra — Syria's most famous UNESCO world heritage site.

Irina Bokova says Palmyra, famous for its 2,000-year-old ruins, should not become the target of any military activity. She spoke to reporters in Beirut after meeting with Prime Minister Tammam Salam on Friday.

Activist groups such as the Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees say that Syrian government warplanes are attacking positions of the Islamic State group on the eastern edge of Palmyra.

They are also reporting fighting on the ground.

Damascus has urged the international community to protect Palmyra from IS, which recently destroyed several archaeological sites in neighboring Iraq.