(CNN) -- United Nations peacekeepers were attacked on the Golan Heights on Saturday, even as U.N. officials said they were working to gain the release of dozens of others detained by Islamist fighters.
The United Nations did not identify who carried out the attacks, but an Israeli military official told CNN that a separate incident -- the capture of 44 peacekeepers in the same area -- was carried out by militants from Syria.
Those holding the peacekeepers are members of the al Qaeda-linked al-Nusra Front, one of the rebel groups fighting President Bashar al-Assad's government, an Israeli military official told CNN on condition of anonymity.
The peacekeepers were detained by al-Nusra following a battle with Syrian forces for control of a checkpoint on the Syrian border of the Israeli-occupied Golan Heights.
The United Nations Disengagement Observer Force has been in place in the Golan Heights since 1974 to maintain a ceasefire between Israel and Syria.
While the United Nations reported 44 had been detained, Al-Nusra released pictures online Saturday that purport to show 45 peacekeepers and their U.N. identification cards. The United Nations has not released the identities of the peacekeepers, and CNN cannot independently confirm the claim by the group.
The details about the detained peacekeepers came the same day that attackers fired on two U.N. positions, the world body said.
The U.N. said no peacekeepers were injured in Saturday's attacks.
One U.N. position was fired upon, resulting in the 32 Filipino personnel there being moved to safety, the U.N. said.
A second position of peackeepers in the Golan Heights was hit with mortar and heavy machine gun fire, the U.N. said. The peacekeepers returned fire and repelled the attackers, but the group remains under fire, the world body said. It later said that 40 Filipino peacekeepers were safe.
The ongoing fire is preventing these peacekeepers from safely pulling back, the United Nations said.
A third outpost of peacekeepers was withdrawn as a precaution after some firing near them.
U.N. Secretary-General Ban Ki-moon condemned the attacks and demanded the "unconditional and immediate release" of the detained peacekeepers.
The peacekeepers from Fiji were captured this week near Quneitra border crossing with the Israeli-occupied Golan Heights.
Al-Nusra Front fighters and other Syrian rebels seized control of the Syrian side of the Quneitra crossing Wednesday -- a capture that represents a new dynamic in a war long feared not only for its deadly effects inside Syria but for threatening to widen into a destabilizing regional conflict.
The peacekeepers "are safe and in good health," the United Nations said Friday, citing "credible sources" since its officials had not yet talked directly with those being held.
Israel seized control of the Golan Heights during the 1967 Six-Day War and fought off an attempt by Syria in 1973 to retake the rocky plateau.
In 1981, Israel annexed the Golan Heights. It is considered to be occupied territory by the international community.
CNN's Pierre Meilhan and Mariano Castillo contributed to this report.