Armed men broke into a U.N. outpost in a buffer zone separating Israel and Syria and abducted three U.N military observers, the U.N. peacekeeping chief said Thursday. Herve Ladsous told a group of reporters that the unarmed observers were held by the Syrian men for about five hours and released unharmed Wednesday morning. It was the third abduction of U.N. peacekeepers in the tense region since March and underlined again their vulnerability in the spillover of the conflict in Syria, which is now in its third year. Ladsous called the latest abduction "a very serious incident ... that illustrates the very difficult conditions that now prevail" in and around the area separating Syrian and Israeli forces which is supposed to be free of armed groups. The U.N. Security Council strongly condemned the abduction of the three observers by "a group of anti-government armed elements" who also looted the observation post. In a statement Thursday evening, the council called on all Syrian parties to cooperate with U.N. peacekeepers, ensure their security, and enable them to operate freely. Ladsous said that early Wednesday morning, a group of unknown unarmed men broke into U.N. Observation Post 52 in the area of separation and abducted three members of Observer Group Golan, which is part of the U.N. Truce Supervision Organization, known as UNTSO. They were released unharmed about five hours later and returned safely to the observation post, where they were met by the head of the U.N. Disengagement Observer Force, known as UNDOF, Ladsous said.