More than 1.2 million Syrians joined anti-regime protests in the northern city of Hama and Deir Ezzor in the east on Friday, the head of the Syrian Observatory for Human Rights said.
"More than 1.2 million people marched: in Deir Ezzor there were more than 550,000, and in Hama more than 650,000," Rami Abdel Rahman said, adding the security forces were notable by their absence during the protests.
In Hama, 210 kilometres (130 miles) north of Damascus, demonstrators chanted slogans "in favour of national unity and against sectarianism," while also calling "for the fall of the regime," Abdel Rahman said.
The authorities are trying to quell protests in the city where rights groups said 25 civilians were killed by the security forces last Friday. Hama has seen some of the largest recent protests against President Bashar al-Assad's regime.
Memories in Hama remain strong of a 1982 crackdown by the President's father, Hafez al-Assad, against Islamists that left 20,000 people dead.
In Deir Ezzor near the border with Iraq, some 430 kilometres east of Damascus, "daily sit-ins are taking place calling for the fall of the regime," Abdel Rahman said.
Syrian television said "about 2,000 people took part in Friday's demonstration in Deir Ezzor, contrary to reports by satellite television channels which put their numbers at hundreds of thousands."