Syrian security forces killed six people on Monday, five during a raid in the flashpoint central province of Homs, as the opposition scrambled to organise against the regime, activists said.
In Geneva, the UN human rights office said the regime's bloody crackdown on protesters is intensifying.
President Bashar al-Assad's forces pursued their repression of anti-regime protesters, killing five in the town of Houla, a Kurdish youth in the province of Latakia, and conducting arrests elsewhere.
"Five residents, including a woman, were shot dead on Monday by security forces, who have been conducting a sweep in Houla since Sunday," the Syrian Observatory for Human Rights said in a statement.
Later it reported that a "Kurdish youth was martyred in the village of Maruniyat (Latakia province) during a raid by security forces."
Security forces also fired on demonstrators in two other towns in Homs, and made arrests in the second city Aleppo, eastern Deir Ezzor and the coastal cities of Latakia and Banias, it said.
The Britain-based Observatory cited an activist at Dhamir in the Damascus area as saying eight defecting soldiers came under intense fire from security forces, with two killed, four arrested and two fleeing.
It said the activist also reported 45 other arrests in Dhamir.
Activists have called for rallies on Tuesday in support of Lieutenant Colonel Hussein Harmush, the first officer to publicly declare his desertion in early June in protest at the crackdown.
On Thursday, state television broadcast an interview with Harmush in which he denied ever receiving orders to shoot civilians.
According to UN estimates at least 2,600 people, mostly civilians, have been killed in the crackdown on pro-democracy protests since March 15.
"Despite the mounting international pressure in the past six months since the start of protests,... the bloody crackdown in Syria has intensified," UN Deputy High Commissioner for Human Rights Kang Kyung-wha said in Geneva.
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Syria "has continuously undermined those promises by more excessive use of force, killing of demonstrators, mass arrests, raids on cities, torture and other abuses," Kang told the UN Human Rights Council.
A fact-finding mission by Kang's office to Syria found that the crackdown may amount to crimes against humanity and urged the UN Security Council to refer the matter to the International Criminal Court.
A Syrian envoy told the council in Geneva the mission's report was "biased" and said "the events that have taken place have nothing to do with peaceful protests."
Assad's government says it is battling "armed terrorist gangs" and will proceed with reforms when Syria is rid of "chaos."
Since mid-March, several opposition groups have emerged united in their call for the regime's ouster but divided about how to do it.
The latest group, the Syrian Coalition of Secular and Democratic Forces (CSDF), meeting in Paris, issued a statement on Monday urging the international community to protect civilians against the repression.
The appeal -- an implicit call for foreign intervention -- conflicted with pleas by other opposition groups for an end to the bloodshed and political, economic and social reforms.
"We call on the international community to adopt a United Nations resolution to protect civilians," said a statement modelled on UN Security Council Resolution 1973 that authorised international action in Libya.
The CSDF brings together a dozen parties and political figures representing non-Islamist opposition groups from Kurdish and Arab, Christian and Muslim communities.
Other opposition groups include the National Coordinating Committee for Democratic Change, a coalition of Arab and Kurdish nationalists, Marxists and independents such as writer Michel Kilo and economist Aref Dalila.
"We need to end the tyrannical security regime. We must overthrow the tyranny and the security (agents)," Hassan Abdel Azim, a senior member of the group said on Sunday.
On Thursday, opposition figures identified members of the "Syrian National Council," revealing the names of just 72 of the 140-strong body for security reasons.
Two more opposition groups were created in Turkey in August -- the mainly Islamist "National Council" and the "National Council of Syrian Transition" headed by Paris-based academic Burhan Ghaliyoun.
French Foreign Minister Alain Juppe said on Monday that "crimes against humanity are committed in Syria. The silence of the Security Council is unacceptable."
Russia -- one of the five permanent Security Council members -- has resisted attempts by the United States and EU nations to issue a resolution condemning Damascus, a key ally and buyer of Russian weapons.