A member of the Al Yarmouk Martyr brigade makes a statement in front of a white UN vehicle in Jamla near Golan HeightsBEIRUT (Reuters) – Syrian rebels have seized a convoy of U.N. peacekeepers near the Golan Heights and say they will grasp them captive unless President Bashar al-Assad's forces pull again from a rebellion-held village which has seen heavy contemporary fighting. The seize was introduced in rebellion videos posted on the Web and proven on Wednesday by means of the United Nations, which said about 20 peacekeepers had been detained. The seizure is essentially the most direct threat to U.N. …