BEIRUT Security forces seized three members of Syria's government-sanctioned opposition shortly after they returned from an official trip to China, a spokesman for the group said on Friday.
Five other members of the National Coordination Body (NCB) were reportedly detained by Syrian security agents on Monday.
Facing a 18-month-old uprising against his rule, President Bashar al-Assad has tolerated some opposition figures who call for a peaceful transition from a one-party state to democratic governance.
NCB spokesman Khalaf Dahowd said NCB foreign affairs head Abdel Aziz al-Khair and executive committee member Eyas Ayyash arrived in Damascus on Thursday night and were followed by Syrian security agents to their car where they joined NCB member Maher Tahan.
"The car never made it to Damascus," Dahowd said. "They were kidnapped and we haven't heard from them since."
The road from Damascus airport to the capital is tightly controlled by state security and there are several checkpoints along the route. Many dissidents have been arrested along it.
The men had returned from a visit to China in which they met Chinese Foreign Minister Yang Jiechi. China has urged Assad to talk to the opposition but has also defended the government, most notably by blocking diplomatic efforts to put pressure on Syria at the U.N. Security Council.
Dahowd said Chinese officials had assured the NCB delegation that Beijing would exert influence over Assad to protect the internal opposition, including a Damascus opposition conference which is planned for Sunday.
"We invited Chinese diplomats in Damascus to the conference to ensure people's lives," said Dahowd on the phone from London.
In July last year, an opposition conference was cancelled after the owner of the venue was threatened by police and security forces fired on a pro-democracy protest outside, killing 14.
Dahowd also said one of the seized men, al-Khair, had been given assurances from Russian Deputy Foreign Minister Mikhail Bogdanov at a meeting in Paris on September 9th that Russia, another country that supports Assad, would back and protect the upcoming opposition conference.
The Russian and Chinese foreign ministries did immediately respond to requests for comment.
"Our group is a group that calls for a peaceful transition. The government knows we are nationalists and that we are not calling for an armed revolt," said Dahowd.
Since the start of the revolt, many of its members had been arrested and killed, he said.
"There is a strong part of the regime who are trying to kill a peaceful solution because they believe this is a conspiracy and they have to sort it out militarily. That's all they've known for 40 years."
Activists say more than 27,000 people have been killed in a conflict which began with peaceful street protests that provoked a military crackdown and mushroomed into civil war.
(Additional reporting by Gleb Bryanski in Moscow; Editing by Angus MacSwan)
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