UNITED NATIONS (AP) — The head of a UN-appointed panel probing alleged war crimes in Syria says the presence of hundreds of militant Islamists threatens to radicalize the 19-month conflict, which is already witnessing a dramatic rise in ethnic tensions.

Brazilian professor Paulo Sergio Pinheiro said at a news conference Tuesday that the panel is afraid these foreign militants and radical Jihadists are not fighting for democracy and freedom but have their own radical agendas.

Pinheiro said human rights violations by both sides have escalated dramatically in recent months though the scale and gravity of the opposition’s violations is less than the government’s.

The panel, appointed by the UN Human Rights Council, recently had its mandate to document, register, and monitor alleged rights violations and war crimes extended until March 2013.