Damascus (AFP) - Syrian authorities have released two prominent members of the domestic opposition who were arrested on Wednesday as they travelled to Riyadh to meet other regime opponents, their party said.

Ahmad al-Asrawi and Munir al-Bitar, members of the National Coordination Committee for Democratic Change (NCCDC), were stopped at Syria's border with Lebanon, said the body's secretary general, Yahya Aziz.

Both Asrawi and Bitar were headed to Saudi Arabia to join fellow members of the opposition's "supreme committee for negotiations," Aziz told AFP.

The "supreme committee" is a 33-member group formed in December at a landmark meeting of Syria's armed and political opposition in Riyadh.

The committee is set to choose at least part of an opposition delegation for peace talks with Syrian President Bashar al-Assad's government next month.

Aziz said Asrawi and Bitar were taken "to an unknown location," adding: "Those who want a political solution would not do this".

The NCCDC later on its Facebook page announced "the release of our colleagues Ahmad al-Asrawi and Munir al-Bitar", calling for "freedom for all prisoners and detainees".

Earlier the group said their arrest contradicted "international efforts to reach a just political solution" to the conflict in Syria.

A statement from the supreme committee said the pair had been due to meet other opposition figures on January 1 to finalise a delegation to negotiate with the government.

"The regime and its allies Russia and Iran are not serious about the political process, (because) they are targeting members of the Riyadh conference that are committed to a political solution," the statement said.

The arrests came less than a week after Syria's army claimed responsibility for the killing of rebel chief Zahran Alloush.

Alloush was the head of Jaish al-Islam, the most powerful rebel faction in Damascus province which had also had taken part in the opposition meeting in Riyadh.

Saudi Foreign Minister Adel al-Jubeir said on Tuesday that the killing did "not serve the peace process and (efforts) to achieve a political solution in Syria".

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He appeared to blame Moscow, a key backer of Assad that has carried out three months of air strikes against rebels in Syria, saying: "I don't know what the Russians have in mind."

Syria's government has regularly referred to Jaish al-Islam and Alloush as "terrorists," but has said it is ready to participate in new peace talks.

On Wednesday, Prime Minister Wael al-Halqi said Syria was "ready to take part in Geneva talks next month... without any international interference."