A new development in war-torn Syria. SOUNDBITE: U.N. HUMAN RIGHTS INVESTIGATOR PAULO PINHEIRO SAYING: "We consider that one of the most alarming and scary elements of this protracted war." UN investigators say Islamist militants have joined the rebels in the fight against President Bashar al-Assad. U.N. Human Rights Investigator Paulo Pinheiro. SOUNDBITE: U.N. Human Rights Investigator Paulo Pinheiro saying: "They are not fighting for the same objectives as the armored groups of the Free Syrian Army. They have their own agenda, their own agenda, they are sort of loose cannon. Then we decide to call the attention of the Human Rights Council to this danger." Militants, he says, have also brought a new deadly skillset. SOUNDBITE: U.N. Human Rights Investigator Paulo Pinheiro saying: "We have a suspicion that the use of IED's are the expertise of some of these groups." Pinheiro and his team have interviewed more than 1,100 victims and defectors in the past year. Their latest report comes on a day that saw bombings in the Syrian province of Idlib.