At least 11 people, including Riad Seif, a former MP, have already been detained for attending a meeting of the National Council of the Damascus Declaration, which calls for radical democratic change in Syria.

"Abu Dan's studio in Aleppo was ransacked on January 21 and paintings and canvases were all destroyed," Qorabi said.

Abu Dan, 55, married with three children, is a former political prisoner who spent over 10 years behind bars for belonging to a communist party banned in Syria.

Opposition unity

Last month's meeting drew together 163 activists and established a national council charged with implementing the Damascus Declaration, which has united communist, nationalist, liberal and Kurdish parties.

Syria responded with a wave of arrests which have drawn strong criticism from the United States.

Tony Fratto, a White House spokesman, said: "The Syrian regime cannot expect to be treated as a respected member of the international community while it engages in such systematic repression of its own citizens."

He said the Syrian government was holding more than 4,000 political prisoners.

George Bush, the US president, has applauded the formation of the Damascus Declaration grouping, saying its members "reflect the desires of the majority of Syrian people to live in freedom, democracy, and peace".