(CNN) -- Perhaps as many as six protesters died in Syria Friday as demonstrators took to the streets across the country, according to activist reports.
The Syrian Observatory for Human Rights said at least six were killed and the Local Coordination Committees of Syria reported at least five deaths. The deaths occurred in the cities of Homs and Aleppo in the west, the Damascus suburbs and Idlib province in the northwest.
For months, demonstrators have marched against the government after Friday prayers.
This week, people poured into the streets in Hama in the west, Deir Ezzor in the northeast, and Binnish in the northwest, said Rami Abdulrahman of the Syrian Observatory for Human Rights.
In Homs, an LCC representative said, the army was heavily deployed in protest hotspots such as Bab Dreib, the Al Fakhoura district, the Al Alawia district, and Bab Sbaa. Friday prayers were prevented in some mosques, including Al Mrayjeh mosque in Bab Sbaa and Al Qasimi mosque in the city's old Souk.
There have been clashes in the city for days, and Thursday Syrian government forces killed about 10 people, according to the LCC, an affiliation of groups that organizes and reports on protests in Syria.
Mosques in Damascus were almost empty after a series of raids and arrests in the capital.
There were some protesters, but the security actions kept masses from marching in the streets. Military forces were searching cars and checking identities at checkpoints in the Damascus areas of Rukn al-Deen and Qaboon, the group said.
There was also a heavy security presence in Daraa in the south. The military surrounded the main mosques but some men were able to go out in small groups. Heavy gunfire was heard, according to the activists.
The developments could not be independently confirmed. Independent accounts of the situation in Syria are hard to come by; most of the international media have been barred from the country.
The Human Rights Watch said Syrian security forces have intensified their campaign of mass arrests in cities that have had anti-government protests.
The cities include Hama, Homs and suburbs around Damascus, the group said.
Citing "reliable activists and witnesses," it estimated that security forces have arrested more than 2,000 anti-government protesters, medical professionals caring for wounded protesters and people alleged to have given information to international news media and human rights organizations.
The LCC, estimates that more than 15,000 people arrested since the beginning of the protests remain in detention, Human Rights Watch said.
The organization said it had "already documented widespread torture from the accounts of people who have been released, causing concern that many detainees still in detention are being tortured."
The unrest in Syria began in mid-March after teens were arrested for writing anti-government graffiti in the southern city of Daraa, according to Amnesty International.
As the clashes intensified, demonstrators changed their demands, from calls for freedom and an end to abuses by the security forces to calls for the regime's overthrow.