Syrian troops and security forces on Monday launched an assault on the central cities of Hama and Homs, where they shot dead at least two people, activists said.
"More than 30 military vehicles and security forces raided Hama this morning and heavy gunfire was heard in the city," Omar Idlibi, spokesman of the Local Coordination Committees, told AFP in Nicosia on the telephone.
A similar operation was carried out in central Homs, where the security forces shot dead at least two people, he added.
Troops backed by tanks had stormed Hama on July 31, on the eve of the start of the holy Muslim month of Ramadan, to fight "armed groups". At least 100 people were killed, and the troops withdrew 10 days later.
The protest hub of Homs also witnessed violence Sunday as 15 people were wounded when troops and security forces raked gunfire in the central city as part of an operation launched Saturday night, activists said.
Elsewhere, at least 24 people were killed in violence across the country on Sunday as the visiting head of the Red Cross, Jakob Kellenberger, sought access to those detained in more than five months of anti-regime protests.
Kellenberger is due to leave the country on Monday afternoon.
Arab League secretary general Nabil al-Arabi said Syrian authorities now agreed to a visit, which he had announced a week ago after the 22-member bloc had met to discuss the Syrian crisis.
More than 2,200 people have been killed in Syria since almost daily protests began on March 15, according to the United Nations, while human rights groups say more than 10,000 people are behind bars.