BEIRUT -- A group of Syrian Greek Orthodox nuns reportedly seized by rebels from a convent near Damascus denied in a video broadcast Friday that they had been kidnapped and said they were being held in a safe place.

It was the first appearance by the nuns, whose alleged Monday abduction has increased concerns about the treatment of Christians by hard-liners in the rebel ranks, particularly as the fighting has engulfed more Christian villages in recent months.

Also Friday, an international watchdog said it has verified the destruction of all of Syria's declared stocks of unfilled munitions for delivering chemical agents, another milestone along the road to eradicating President Bashar Assad's chemical weapons program.

The Organisation for the Prohibition of Chemical Weapons said in a statement that its experts in Syria also have verified the destruction of parts of buildings at weapons production facilities.

The latest destruction work was near the city of Homs -- sites that the OPCW said had been inaccessible due to security reasons. The Syrian army has been advancing against rebels and on Monday troops reopened the highway linking Damascus with the central city of Homs.

The highway is a key road leading to Syria's coast and could open the way for transporting the country's chemical weapons to be sent to the port of Latakia before they are taken out of the country for destruction.

The joint United Nations-OPCW team in Syria aims to remove most chemical weapons from Syria by the end of the year for destruction at sea and destroy the entire program by mid-2014. The unprecedented disarmament in the midst of a civil war was launched following an Aug. 21 chemical weapons attack on a Damascus suburb that killed hundreds of civilians.

The U.S. and Western allies accused the Syrian government of being responsible for that attack, while Damascus blames the rebels. Syria joined the OPCW and agreed to dismantle its chemical arsenal to ward off possible U.S. military strikes.

In another positive development for the mission, Denmark and Norway confirmed that they would offer to help transport "chemical warfare agents" out of Syria using specialized cargo vessels and naval frigates.

"The use of chemical weapons is a threat to international peace and security," Norwegian Foreign Minister Borge Brende, and acting Danish Foreign Minister Rasmus Helveg Petersen said in a joint statement. "Removal of these heinous weapons from Syria is a critical task for the international community."

Both countries had earlier said they would help ship the chemicals, but the announcement highlighted that the Scandinavian neighbours are planning a joint mission led by Denmark. Both countries said they will have to "complete relevant national procedures before the operation can begin."

In the video aired by the Qatar-based Al-Jazeera satellite channel Friday, the Greek Orthodox nuns appeared healthy. They sat on sofas in a "villa" at an undisclosed location, and took turns speaking, saying they were escorted out of Maaloula to keep them safe from the shelling.

"The brothers are treating us well and have brought us from the convent here and we are very happy," one of them says to the camera. The video appeared authentic, but it was impossible to independently verify it or to know if the nuns were speaking under duress.

The Britain-based Syrian Observatory for Human Rights and religious officials had said the Orthodox nuns and three civilians were taken by rebels from the Mar Takla convent in Maaloula after rebels overran the village, and were being kept in the nearby rebel-held town of Yabroud.

Pope Francis has called for prayers for the nuns.

Christians and other minorities tend to support the government of Assad, who comes from a Shiite offshoot sect. They are concerned about the rising role of al-Qaida-linked group in the rebel movement, dominated by Syria's Sunni Muslim majority. The hard-liners have been accused of vandalizing churches and abducting several clerics.

Greek Catholic Patriarch of Antioch Gregorios III Laham, commenting on the video, thanked all who contributed to making the nuns comfortable, but said: "Real comfort would be in their homes." His comments were published in Lebanon's official National News Agency.

Also Friday, a suicide car bomber detonated his explosives near a building manned by paramilitary forces in a mainly Kurdish town in northeastern Syria, killing at least five people, according to the state news agency and activists.

The blast in Qamishli follows clashes between Kurdish gunmen and Islamic militant groups led by the al-Qaida-linked Islamic State of Iraq and the Levant that left hundreds of people dead in recent months.

Kurds are the largest ethnic minority in Syria, making up more than 10 per cent of the country's 23 million people.

Syria's state news agency SANA said the explosion occurred on a crowded street in Qamishli, which is in Hassakeh, killing six people and wounding 30.

The Observatory, which has a network of activists around the country, said the attack targeted a building manned by pro-government gunmen known as National Defence Forces. It said the blast killed at least five and wounded 10.

The Observatory said it is not clear if the dead were members of the National Defence Forces.