Syrian security forces have shot dead at least 800 civilians since pro-democracy protests erupted seven weeks ago, Syrian rights groups Sawasiah said on Saturday.
The organization, which was founded by jailed human rights lawyer Mohannad al-Hassani, said in a statement sent to Reuters it had the names of the 800 civilians killed. Among them were 220 killed in a tank-backed army attack on the city of Daraa.
On Saturday, Syrian tanks stormed the mostly Sunni city of Banias, a rights campaigner said, raising sectarian tensions in a country swept by protests against the rule of President Bashar Assad, an Allawite.
At least six civilians were killed in the attack, including four women, human rights campaigners said.
The Syrian Observatory for Human Rights confirmed the death toll. The Observatory said the six where killed during the attack on Banias and demanded the Syrian authorities allow an independent committee to investigate the deaths.
The attack on Banias came hours after the United States, reacting to the death of 27 protesters on Friday, threatened to take new steps against Syria's rulers unless they stopped killing and harassing their people.
The army entered Banias, a coastal city of 50,000 people, from three directions, advancing into Sunni districts but not Alawite neighbourhoods, the campaigner said.
Most communication with Banias has been cut but the campaigner said he was able to contact several residents.
"Residents are reporting the sound of heavy gunfire and seeing Syrian navy boats off the Banias coast. Sunni and mixed neighborhoods are totally besieged now," said the campaigner, who did not want to be identified.
Banias has seen some of the most persistent demonstrations since an uprising erupted in the southern city of Daraa seven weeks ago demanding political freedom and an end to corruption.
Authorities said the coastal city was a "center of Salafist terrorism" and said armed groups had killed soldiers near the city. Salafism is an ultra-conservative brand Sunni Islam.
Civic leaders in Banias, issued a statement denying the accusation and saying the authorities were trying to spread fear among Alawites, who occupy most senior positions in the army and security apparatus.
Assad said the protesters were part of a foreign conspiracy to cause sectarian strife.
His father Hafez Assad brutally suppressed an armed Islamist uprising in 1982 in which 30,000 people were killed.
Mostly Sunni districts of Banias have been under the control of protesters since Assad loyalists, known as "al-shabbiha", fired at residents from speeding cars on April 10, after a large demonstration that demanded the "overthrow of the regime".
International criticism has mounted against Assad, who is trying to maintain his family's four-decade grip on power in the country of 20 million.
European Union governments agreed on Friday to impose asset freezes and travel restrictions on up to 14 Syrian officials and to impose sanctions in response to Assad's violent crackdown.
The United States imposed sanctions of its own last week against some figures in the Syrian government. On Friday it threatened to step up the pressure to try to stop the violence.
Officials give a lower death toll and say half the fatalities have been soldiers and police, blaming "armed terrorist groups" for the violence. They say demonstrators are few in number and do not represent the majority of Syrians.
"The United States believes that Syria's deplorable actions toward its people warrant a strong international response," White House press secretary Jay Carney said in a statement.
"Absent significant change in the Syrian government's current approach, including an end to the government's killing of protesters ... the United States and its international partners will take additional steps to make clear our strong opposition to the Syrian government's treatment of its people."
Protests broke out after Friday prayers in cities across Syria, from Banias on the Mediterranean coast to Qamishly in the Kurdish east, demanding an end to Assad's autocratic rule.Friday's bloodiest confrontation was in the city of Homs where 15 protesters were killed, activist Ammar Qurabi said.
State news agency SANA said on Saturday that "terrorist groups" had killed 11 soldiers and policemen in Homs, listing the names of those dead. The figure was put at 5 on Friday.
Wissam Tarif an activist outside Syria said witnesses told him nine soldiers defected in Homs to the protesters and may have clashed with other troops.
Four protesters were killed by security forces in Deir al-Zor, a local tribal leader said, the first deaths reported from the region which produces most of Syria's 380,000 barrels
per day of oil in seven weeks of unrest.
A Western diplomat said 7,000 people had been arrested since the demonstrations broke out on March 18 in Daraa, where an ultra-loyalist division led by Assad's brother Maher shelled and machinegunned the old quarter last Saturday, residents said.
The United States condemned the assault as "barbaric".
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