Tens of thousands of Syrians have again taken to the streets for Friday protests, in defiance of the massive crackdown against them.
One human rights activist thought as many as 1.2 million people were taking part across the country.
Security was tight in the capital Damascus, with checkpoints set up, communications cut and arrests made.
There are reports of gunfire and tear gas being used against several demonstrations.
Activists say at least one person has been killed in Aleppo in north-west Syria, and another in the central city of Homs.
Police reportedly used batons as well as tear gas break up a protest in the mainly-Kurdish city of Qamishli.
Marches were also taking place in other Kurdish towns, in the eastern city of Deir Ezzor, in the southern town of Sueweida and in the north-west province of Idlib.
There were also reports of demonstrations in Homs, 160km (100 miles) from Damascus, which has been subject to a massive military crackdown in recent days.
Activists say at least 50 people have been killed in Homs - which has been at the heart of the four-month uprising - since Saturday.
Observers say the heavy military presence in Damascus is in response to last Friday, which saw some of the largest protests since the anti-government uprising began in March. Around 30 people were killed.
The Syrian Observatory for Human Rights said the districts of Qabun and Rukneddin had a heavily military presence, with barricades and checkpoints set up at entrances and exits.
"Rukneddin is completely isolated," the group's Rami Abdel Rahman told the AFP news agency. "Thousands of security officers are patrolling and conducting searches of homes and making arrests."
One activist in Damascus, Abu, told the BBC that communications and electricity in Harasta and Duman districts have been switched off.
He said that the security agents appeared to be changing tactics - "kidnapping people from streets and coffee shops" rather than arresting activists in their homes.
And Abu predicts the crackdown will increase in the lead up to Ramadan.
"Ramadan is soon and, in Ramadan, each day is like a Friday," he said. "We believe the government is trying to stop the activists before Ramadan."
International journalists have been denied access to Syria so it is difficult to verify reports.
Human rights groups say that about 1,400 civilians and 350 security forces personnel have died in the four months of protest.
The government blames the unrest on "armed criminal gangs" backed by a foreign conspiracy.