By Suleiman Al-Khalidi AMMAN (Reuters) - Islamic State militants have abducted at least 90 people from Assyrian Christian villages in northeastern Syria, a monitoring group tracking violence in Syria said on Tuesday. The British-based Syrian Observatory for Human Rights said they carried out dawn raids on rural villages inhabited by the ancient Christian minority west of Hasaka, a city mainly held by the Kurds. Syrian Kurdish militia launched two offensives against the militants in northeast Syria on Sunday, helped by U.S.-led air strikes and Iraqi peshmerga. This part of Syria borders territory controlled by Islamic State in Iraq, where it committed atrocities last year against the Yazidi religious minority.