AMMAN - Islamic State has withdrawn some of its insurgents and equipment from areas northeast of the Syrian city of Aleppo, rebels and residents say, adding to signs of strain in the Syrian provinces of its self-declared caliphate.The group, which has recently lost ground to Kurdish and Syrian government forces elsewhere in Syria, has pulled fighters and hardware from several villages in areas northeast of Aleppo, they said. But it has not fully withdrawn from area.The Syrian Observatory for Human Rights, which tracks the war using a network of sources on the ground, said Islamic State had redeployed forces from Aleppo province to join battles further east with Kurdish forces and mainstream rebel groups.Islamic State-held areas northeast of Aleppo mark the western edge of a domain that expanded rapidly in Syria and Iraq last year after the jihadists seized the Iraqi city of Mosul.Last month, the group suffered its first major setback in Syria since last summer, being driven from the predominantly Kurdish town of Kobani by Kurdish militia backed by US-led air strikes. Syrian government forces waging a separate campaign against the group have also inflicted losses on it recently."There are tactical withdrawals. It's not a complete withdrawal," said the leader of a mainstream rebel group, citing contacts in Islamic State-held areas near Aleppo. Other groups had not moved to take the evacuated areas because Islamic State had not fully pulled out, he added.