BEIRUT - Rebels holding 21 UN peacekeepers near the Golan Heights in southern Syria say government forces must leave the area before they free their "guests," an activist in touch with the fighters said on Thursday.Rami Abdelrahman of the Syrian Observatory for Human Rights quoted a spokesman for the "Martyrs of Yarmouk" rebel brigade as saying the peacekeepers were being held as "guests" in the village of Jamla, about a mile (1.6 km) from a ceasefire line with the Golan Heights."He said they will not be harmed. But the rebels want the Syrian army and tanks to pull back from the area," Abdelrahman said after speaking to the rebel spokesman on Thursday morning.Yarmouk is the name of a Palestinian refugee camp in Damascus, however it is not yet known if it is linked to the group.The capture of the UN peacekeepers close to Israeli-held territory was another sign that Syria's conflict, nearing its second anniversary, could spill over to neighboring countries.Israel has said it will not "stand idle" if violence spreads to the Golan, which it captured in the 1967 Middle East war.Suspected Sunni Muslim insurgents killed 48 Syrian troops inside Iraq on Monday and cross-border artillery fired from Syria has killed people in Lebanon and Turkey in recent months.Inside Syria itself, the United Nations says around 70,000 people have been killed in the uprising which erupted in March 2011 with mainly peaceful protests against Syrian President Bashar Assad and has spiraled into an increasingly sectarian conflict.The Philippine government condemned the capture of the peacekeepers - three officers and 18 enlisted men - which it called a "gross violation of international law."President Benigno Aquino told reporters the peacekeepers were being well treated and that the United Nations was in touch with the rebels to ensure their safety. "By tomorrow they expect all of these 21 to be released," he said, adding their release might occur as early as Thursday.Aquino said both sides in the Syrian conflict considered the United Nations a "benign presence" in the country - a view not shared by many Syrian rebels, who hold the organization at least partly responsible for a lack of international support.In a video released to announce the capture of the UN convoy on Wednesday, a member of the Yarmouk Martyrs' Brigade accused the peacekeepers of collaborating with Assad's forces to try to push them out of village of Jamla which the rebels seized on Sunday after heavy fighting.Human Rights Watch said it was investigating the Yarmouk Martyrs for involvement in past executions, including a videotaped killing of Syrian soldiers which was posted on the Internet on Tuesday.One video showed rebels with several men in army fatigues they said were captured at a Syrian army base near Jamla. Another video showed 10 dead men, including some of the captives filmed alive in the earlier video. Peacekeepers of the UN Disengagement Force (UNDOF) mission have been monitoring a ceasefire line between Syria and the Israeli-occupied Golan Heights, for nearly four decades.The UN Security Council and Secretary-General Ban Ki-moon condemned the seizure of the observers and demanded their immediate release."The UN observers were on a regular supply mission and were stopped near Observation Post 58, which had sustained damage and was evacuated this past weekend following heavy combat in close proximity at Al Jamla," the United Nations said, referring to a village which saw fierce clashes on Sunday.It said the peacekeepers were taken by around 30 fighters.In one rebel video, a young man saying he was from the Martyrs of Yarmouk brigade stood surrounded by several rebel fighters with assault rifles in front of two white armored vehicles and a truck with "UN" markings."The command of the Martyrs of Yarmouk ... is holding forces of the United Nations Disengagement Observer Force until the withdrawal of forces of the regime of Bashar Assad from the outskirts of the village of Jamla," he said.At least five people could be seen sitting in the vehicles wearing light blue UN helmets and bulletproof vests. "If no withdrawal is made within 24 hours we will treat them as prisoners," the man said.