The Syrian opposition has urged authorities in neighbouring Lebanon to act over reports that more than a dozen of their members in that country have been kidnapped.
"The executive board of the Syrian National Council has expressed its concern in a letter sent to Prime Minister Najib Mikati in light of reports by rights groups that 13 Syrian nationals have been kidnapped," the opposition group said in a statement late on Tuesday in Beirut.
It said that among those kidnapped was Shebli al-Aysami, 86, who was last seen in Lebanon in May.
"The Council if very worried that opposition members are being handed over to the Syrian security services and as such risk death," the statement said.
It urged the Lebanese government, whose cabinet is dominated by the Syrian-backed Hezbollah and its allies, to take all necessary measures to prevent what it called any further kidnappings and to free those still in its custody.
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"Lebanon must not allow the Syrian regime to use its territory for acts of terror and repression against opposition members and must ensure the country remains a safe haven for freedom of expression," the statement said.
Lebanon's police chief last month told a parliamentary committee that he had collected evidence pointing to the involvement of the Syrian embassy in Aysami's disappearance.
Mikati last week acknowledged that opposition figures from neighbouring Syria had been kidnapped in Lebanon, but he downplayed the abductions as isolated incidents.
Aysami is a co-founder of Syria's ruling Baath party but fled his native Syria in 1966 over political differences with the group. He was last seen in the eastern Lebanese region of Aley.
Three Syrian brothers also went missing in March after one of them was seen in Beirut distributing tracts for a demonstration against the regime in Damascus.
According to Lebanese authorities, some 5,000 Syrians have sought refuge in Lebanon since the outbreak of the revolt in Syria last March.