The United Nations said Wednesday that 20 peacekeepers had been detained by a group of 30 armed fighters near the Golan Heights on the border between Syria and Israel.
U.N. deputy spokesman Eduardo del Buey said the U.N. observers were on a regular supply mission when they were stopped near an observation post that sustained damage and was evacuated last weekend following heavy combat.
He said the U.N. peacekeeping mission, known as UNDOF, has dispatched a team to assess the situation and attempt a resolution.
The U.N. Security Council strongly condemned the detention of the peacekeepers and demanded their immediate and unconditional release.
Earlier Wednesday, videos surfaced purporting to show Syrian rebels holding the seized U.N. convoy, Reuters reports.
The videos show several armed rebel fighters surrounding two white vehicles with "UN" written on them and at least five people wearing United Nations light blue helmets.
In one of the videos, a man saying he was from the "Martyrs of Yarmouk" brigade said the U.N. convoy would not be released until forces loyal to embattled Syrian President Bashar Assad withdrew from the village of Jamla, Reuters reports.
"If no withdrawal is made within 24 hours we will treat them as prisoners," said the man, who was dressed in civilian clothes.
The group Human Rights Watch says it has been investigating the "Martyrs of Yarmouk" and their suspected involvement in a videotaped execution of detained Syrian soldiers posted on the Internet on Tuesday, Reuters reports.
The U.N. force was established in 1974 following the 1973 Yom Kippur war to monitor the disengagement of Israeli and Syrian forces and maintain the cease-fire. Israel captured the Golan Heights from Syria in 1967 and Syria wants the land returned in exchange for peace.
U.N. Secretary-General Ban Ki-moon has warned of escalating military activity along the Israeli-Syrian border as a result of the intensifying Syrian conflict, which has gone on for two years and cost more than 70,000 lives.
In December, Ban accused the Syrian government of serious violations of the 1974 separation agreement and called on both countries to halt firing across the cease-fire line. He also cited numerous clashes between Syrian security forces and opposition fighters in the disengagement zone.
In response, he said, UNDOF has adopted a number of security measures.
The Associated Press contributed to this report.