BEIRUT (AP) -- New video Thursday of U.N. peacekeepers held captive by Syrian rebels illustrates the sudden vulnerability of a U.N. force that had patrolled a cease-fire line between Israel and Syria without incident for nearly four decades.
The abduction of the Filipino troops -- soft targets in Syria's civil war -- also sent a worrisome signal to Israel about the lawlessness it fears along the shared frontier if Syrian President Bashar Assad is ousted.
Opposition fighters seized the 21 peacekeepers Wednesday near the Syrian village of Jamlah just a mile from the Israeli-controlled Golan Heights, a plateau Israel captured from Syria in 1967.
Negotiations were under way Thursday for the release of the men, who said in videos posted online that they were being treated well.
"To our family, we hope to see you soon and we are OK here," said a peacekeeper shown in one video. He was one of three troops dressed in camouflage and blue bullet-proof vests emblazoned with the words U.N. and Philippines.
However, a rebel spokesman seemed to suggest the hostages were also serving as human shields. If the U.N. troops are released and leave the area, the regime could kill "as many as 1,000 people," said the spokesman, who spoke via Skype and did not give his name for fear of reprisals.
The peacekeepers' abduction highlights the growing risks to U.N. staff in Syria's escalating conflict.
Fighting has spread across the country, claiming more than 70,000 lives and displacing nearly 4 million of Syria's 22 million people. There is no sign of a breakthrough for either side, though rebels have scored some recent gains on the battlefield and in the diplomatic arena.
U.N. diplomats and officials said Thursday that the capture of the 21 peacekeepers will almost certainly lead to a re-examination of security for the U.N. monitors and their patrols in the field.
The U.N. mission, known as UNDOF, was set up in 1974, seven years after Israel first captured the Golan and a year after it managed to push back Syrian troops trying to recapture the territory in another regional war.
For nearly four decades, the U.N. monitors helped enforce a stable truce between Israel and Syria, making it one of the most successful U.N. missions in the world, said Timor Goksel, a Beirut-based former senior U.N. official in the region.
The force has an office in Damascus and staffs observation posts along the armistice line. The peacekeepers shuttle between Damascus and the outposts to deliver supplies and rotate crews.
Goksel, who works for the Al-Monitor news website, said the observers are "soft targets" in Syria's increasingly brutal civil war. Up to now they were "never challenged by anybody in Syria," he added.
The monitors' success may have been linked to a decision by Assad and his father and predecessor Hafez Assad to comply with the armistice deal, including limits on military hardware allowed near the cease-fire line.
Moshe Maoz, an Israeli expert on Syria, said the U.N. mission's success was largely due to the Assads' decision to abide by the truce.
"When you are dealing with an army that follows orders, it is one thing," Maoz said. "Now you have different groups. They do not recognize international law and have no respect for any law or international morals. They are terrorist groups that know no bounds."
An Israeli official said that if UNDOF were to halt operations, it would be a "bad thing for peace." He spoke on condition of anonymity because he was not authorized to discuss the diplomatically sensitive issue with the media.
Israel has said it's trying to keep out of the Syria conflict, but is watching the disintegration of the country with growing concern.
In recent months, Syrian mortars overshooting their target have repeatedly hit the Israeli-controlled Golan. In Israel's most direct involvement so far, Israeli warplanes struck inside Syria in January, according to U.S. officials who said the target was a convoy carrying anti-aircraft weapons bound for Hezbollah, a Lebanese militia allied with Assad and Iran.
The peacekeepers' four-vehicle convoy was intercepted Wednesday by rebels from a group calling itself the Martyrs of the Yarmouk Brigades. The convoy was stopped on the outskirts of Jamlah, about a mile from the armistice line.
Rebels said 10 people have died in regime shelling of Jamlah and nearby villages in recent days. Fighting continued Thursday, according to activists.
The rebels and Syrian opposition officials have sent conflicting messages about the peacekeepers' release.
Immediately after the convoy was stopped, one of the rebels said the U.N. troops would be held until regime forces leave Jamlah.
A member of Syria's political opposition in exile, Khaled Saleh, said the rebels would deliver the U.N. troops to safety in Jordan as soon as the regime halts airstrikes in the area and a transfer is deemed safe.
In two amateur videos posted Thursday, men who appeared to be captive U.N. troops made similar statements, though it was not clear to what extent they had been coerced to do so.
"We, the U.N. personnel here, are safe, and the Free Syrian Army are treating us good," one of three peacekeepers shown in the video said in halting English. "We cannot go home because the government of (President Bashar) Assad do not stop the bombing."
In another video, six men, presumably peacekeepers, are shown. One man, who identifies himself as a captain, said the U.N. force encountered bombings and artillery, and civilians in the area "helped us for our safety."
The videos appear in line with AP reporting of the incident.
The U.N. Security Council has demanded the peacekeepers' immediate and unconditional release.
In Washington, State Department spokeswoman Victoria Nuland called the men's continued detention "absolutely unacceptable."
The Britain-based Syrian Observatory for Human Rights, an activist group, said negotiations were under way between the rebels, the Arab League and U.N. officials on handing over the peacekeepers. As part of the negotiations, the rebels were demanding that the regime withdraw from the area, end shelling attacks and allow refugees to return, the Observatory said.
Meanwhile, Nuland said Assad's forces have bombarded opposition-held neighborhoods in the central city of Homs in the last 24 hours and cited reports that regime forces were amassed outside of the city "for what looks to be an all-out assault on rebel holdouts."
Associated Press writers Bassem Mroue in Beirut, Aron Heller in Jerusalem, Edith M. Lederer at the United Nations and Bradley S. Klapper in Washington contributed to this report.