Syrian security forces arrested George Sabra, a key opposition figure, in his house in Damascus early Wednesday, according to activists, dpa reported.
This is the second time Sabra, a senior member of the National Democratic Party, has been detained since pro-democracy protests started in Syria in March, said the Local Coordination Committees of Syria (LCCS).
They added that the Syrian forces carried out a campaign of "arbitrary" arrests in several areas across the country, including suburbs in Damascus and the central city of Homs.
At least 16 people were killed in Homs on Tuesday when members of the security force opened fire at mourners during a funeral of 10 people killed Monday in anti-government demonstrations, a Syrian activist based in Damascus told the German Press Agency dpa.
On Wednesday, Syrian Foreign Minister Walid al-Moallem called on Europe to change its policy towards Syria in order to "preserve its interests and stability in the region."
"If Europe wants to return to the map, it has to change its current policy towards Syria," al-Maollem said at a seminar in Damascus.
In June, al-Moallem said that his country would forget that "Europe exists on the map."
His remarks came after the EU imposed sanctions on Syrian officials, including President Bashar al-Assad, over the draconian crackdown on pro-democracy protesters.
Criticizing what he termed as the American interference in Syrian affairs, al-Moalem Wednesday accused the United States of acting at the behest of Israel.
"The US policy is made in Israel," he added.
Earlier this month, the US ambassador to Syria visited the central city of Hama, which has been the scene of mass protests against the rule of al-Assad.
More than 1,400 people have been killed by security forces since protests began in Syria in mid-March, according to Syrian-based human rights advocates.
The government disputes the figure and blames "armed thugs" and foreign conspirators for the unrest.
The reports are hard to verify as the Syrian authorities have barred most foreign media and international human rights groups from entering the country.