The United Nations said Thursday 43 of its peacekeepers had been captured by an armed group on the border with Syria and Israel, and another 81 are unable to leave their positions near the border crossing.
Militants with the Islamist al-Nusra front on Wednesday stormed the border post. It was unclear who was holding the U.N. personnel.
In a statement, the U.N. said it was making every effort to secure the release of its peacekeepers and restore freedom of movement for the others.
Intense fighting in Syria has occasionally spilled over the border, with mortars landing near U.N. positions on the Israeli-controlled side of the Golan Heights.
In New York, U.N. Assistant Secretary-General Kyung-wha Kang said that in the face of total impunity, human rights violations by all parties have become the norm in Syria.
She said the advancement of the Islamic State extremist group into central Syria was taking the violence against unprotected civilians to a "new level," including people being beheaded, crucified, and sold.
The Syrian government has increased its indiscriminate use of barrel bombs in residential neighborhoods where civilians do not have the means to leave, while opposition groups using mortar attacks and bombs are killing and injuring scores of people, including children.
Kang said some 240,000 people remain under siege in Syria and aid deliveries are constantly being blocked or delayed.
As of July 31, 1,223 U.N. peacekeepers from from Fiji, India, Ireland, Nepal, Netherlands and Philippines monitored the border.
Citing security concerns, the Philippines last week said it would bring home its troops in October when their tour of duty ends.
U.N. Disengagement Observer Force peacekeepers were previously detained by armed militants in March and May of 2013, but were released safely.