A Syrian court has reportedly sentenced a leading dissident to 12 years in jail for undermining national security after he visited the US.
Syrian police were awaiting Labwani's return from Washington
Kamal Labwani was arrested in 2005 when he returned to Damascus after meeting US officials in Washington.
The White House and State Department have called on Syria to release Labwani and stop harassing reform advocates.
The verdict follows the jailing of human rights lawyer Anwar al-Bunni, signalling a continued crackdown.
Correspondents say Dr Labwani looked shocked for a few seconds as the judge pronounced the verdict, then gave a faint smile and raised his fist in the air, without speaking.
His wife Samar whispered: "It is too much.
Other stunned relatives in the courtroom murmured, "Allahu Akbar (God is great)."
"I think what we're seeing today is another symbol of the peaceful opposition to the Syria regime being punished for their views," said Nadim Houri, Syria researcher with Human Rights Watch.
The judge reportedly told the court that the charges of contacting a foreign country, passing on messages and encouraging attack against Syria, could have carried a life sentence with hard labour.
The 50-year-old physician has been imprisoned by the authorities in the past for his activities as founder of the Democratic Liberal Gathering.
As usual, there is no confirmation of the sentence from the Syrian authorities, who do not comment on trials related to political or national security issues.
The verdict was announced as President Bashar al-Assad was addressing the Syrian parliament.
He said Damascus would not co-operate with a UN-backed tribunal to try suspects in the killing of former Lebanese Prime Minister Rafik Hariri if it would undermine Syrian sovereignty.
"The abandonment of sovereignty means that Syrian law no longer protects Syrian citizens," Mr Assad said in the televised address.
The Labwani verdict comes a week after a ground-breaking meeting between Syrian Foreign Minister Walid Muallem and US Secretary of State Condoleezza Rice at a summit in Egypt - the first time the two countries held such high-level talks since the death of Mr Hariri in 2005.
The previous week a court jailed Bunni for spreading hostile information and joining an illegal political group, in an ongoing crackdown on advocates of democratic reform in Syria.