Syrian rebels holding 21 U.N. peacekeepers near the Israel's Golan Heights in southern Syria said on Friday no talks were under way to free the men and gave no indication that they would be released soon.
The men are part of the U.N. Disengagement Observer Force (UNDOF), which has been monitoring a ceasefire line between Syria and Israel on the Golan Heights since 1974.
Their capture just a mile from Israeli-held lines is further evidence of how Syria's conflict, nearing its second anniversary, could spill over into neighboring countries.
"There are no negotiations between any parties," said Abu Essam Taseel, from the media office of the "Martyrs of Yarmouk" brigade that captured the Filipino peacekeepers on Wednesday.
In several videos released on Thursday, the peacekeepers said they were being treated well in the village of Jamla by civilians and rebels opposed to President Bashar al-Assad.
The United Nations said the captives had been detained by around 30 rebel fighters, but Taseel said the men were "guests", not hostages, and were being held for their own safety.
However, he said they would only be released once Assad's forces retreated from around Jamla and halted bombing there.
"Negotiations should be between (the United Nations) and the regime of Bashar al-Assad to stop the bombing and lift the blockade of the area so it can be safe," Taseel said.
The Damascus government has not commented publicly about the incident.
The International Committee of the Red Cross (ICRC) said it had been approached by the Syrian opposition and was prepared to play a role in "receiving" the peacekeepers once they are released, but would not get involved in actual negotiations.
The ICRC was ready "to play the role of neutral intermediary in the framework of the kidnapping of the UNDOF soldiers provided that this is agreeable to all the parties concerned," ICRC spokeswoman Dibeh Fakhr told Reuters in Geneva.
INCURSIONS IN DE-MILITARISED ZONE
Taseel said the U.N. observers had a responsibility to keep heavy weapons out of the area.
Under an agreement brokered by the United States in 1974, Israel and Syria are allowed a limited number of tanks and troops within 20 km (13 miles) of the disengagement line.
Taseel said the Syrian military had exceeded those limits and that its warplanes were bombing opposition targets within 500 meters (yards) of the disengagement line.
A U.N. report in December said both the Syrian army and rebels had entered the de-militarized area between Syrian and Israeli forces, and that Syrian army operations had "affected adversely" UNDOF operations.
Referring to incidents including shelling from Syrian territory last year, it said: "Recent incidents across the ceasefire line have shown the potential for escalation of tensions between Israel and the Syrian Arab Republic, and jeopardize the ceasefire between the two countries."
In January, Israel bombed an arms convoy in Syria which may have been destined for its Lebanese foe Hezbollah, diplomats and security sources said. Israel has said it will not "stand idle" if violence spreads to the Golan, which it captured in 1967.
The Israeli army told Reuters that eight UNDOF soldiers were "evacuated into Israel" from their lookout post on Friday, but gave no reason for the move.
The United Nations says around 70,000 people have been killed in Syria in the past two years. An uprising that began with mainly peaceful protests against Assad in March 2011 has spiraled into an increasingly sectarian armed conflict.
Additional reporting by Dominic Evans in Beirut, Stephanie Nebehay in Geneva and Ori Lewis in Jerusalem; Editing by Alistair Lyon and Jon Hemming