Opposition fighters in Syria claim to have kidnapped at least 94 women and children belonging to President Bashar al-Assad's minority Alawite sect, according to a video obtained by Al Jazeera.

In the video, broadcast by Al Jazeera on Thursday, the rebels said they were holding the hostages to secure the release of opposition supporters from government detention.

The civilians were abducted in August from villages in rural Latakia, Assad's coastal stronghold.

Thousands of people are thought to be imprisoned by both sides in the increasingly sectarian civil war, which enters its fourth year this month.

The video said the rebels were ready to swap the civilians for 2,000 prisoners who have been detained for more than a year.

It stipulated that most of the freed prisoners be from coastal areas of the country and that half of them be women and children.

In one scene, three women wearing headscarves and simple clothing address the camera.

Another scene shows dozens of women and children standing outdoors in a walled-in area.

Syria's Sunni Muslim majority has largely joined the revolt against Assad, while minority sects have mostly stood behind him in a conflict that has killed more than 140,000 people.

Both sides in the civil war have targeted citizens and attracted foreign fighters and financial support from across the region.

A rare prisoner swap was achieved last week, securing the release of 13 Greek Orthodox nuns detained since December by fighters from the Nusra Front, al-Qaeda's official affiliate in Syria.

The government freed at least 25 prisoners in exchange.

Qatar said it had played a mediating role in securing the nuns' release, but Syria denied the allegation.

Brahimi's warning

The video of the kidnapped civilians was broadcast on a day the UN-Arab League mediator for Syria said that if the Syrian government went ahead with presidential elections, the opposition would probably refuse to participate in a new round of peace talks.

Lakhdar Brahimi said after briefing the UN Security Council behind closed doors on Thursday that he asked members for their help in making sure that if and when there was a third round of talks in Geneva, "it will be a little bit more productive than the second one".

Brahimi addressed the Security Council soon after Syria's parliament unanimously approved a new election law allowing multiple candidates to run for president and parliament.

At the latest round of talks last month in the Swiss city, Brahimi wanted both sides to hold parallel talks on terrorism, which is a major concern for the government, and the establishment of a transitional governing body for Syria agreed on by major powers at a Geneva conference in June 2012.

The opposition agreed to Brahimi's plan, but according to two diplomats who listened to the closed briefing, Brahimi said the Syrian government used "delaying tactics" and insisted that the terrorism discussion be concluded before talks on a transitional government started.

Bashar Jaafari, the Syrian ambassador, said afterwards that his government agreed to Brahimi's agenda, but he insisted that fighting terrorists, as Syria calls the opposition fighters, is paramount and must be dealt with first.

"After three years of the crisis continuing on the Syrian soil, and after two years of the issuance of the Geneva communique, some delegations in the Security Council finally acknowledged the presence of terrorism in Syria," he said.