Security forces killed at least seven more people in Syria, activists said, urging fresh anti-regime protests on Friday under the banner of "death rather than humiliation."
In Paris, US secretary of state Hillary Clinton said the world community should escalate pressure on President Bashar al-Assad by targeting Syria's oil and gas exports to force him from office.
"The violence must stop and he needs to step aside," Clinton told reporters in Paris after a meeting Thursday on Libya, where strongman Muammar Gaddafi has already been forced from office.
Spanish Prime Minister Jose Luis Rodriguez Zapatero also said the world community should support Syrians opposed to Assad, following the success of UN-backed action in Libya.
"This example should extend to other countries like Syria (where people are) fighting for freedom and to whom the international community should give its wholehearted backing," he said.
A senior Syrian official, meanwhile, said in a contested video posted on YouTube that he has resigned in disgust at hundreds of killings and thousands of arrests by Assad's regime.
The Syrian Observatory for Human Rights said four people -- including an 11-year child -- were killed and several more were wounded Thursday when security forces opened fire on protesters in the central region of Homs.
According to the Local Coordination Committees (LCC), which groups activists on the ground, armoured cars entered the city of Homs itself.
The Britain-based Observatory also reported "one dead and five wounded in an assault by the army and security forces on the village of Al-Rama" in the northwestern province of Idlib, near the Turkish border. The deceased was a man in his seventies.
And the LCC said a young man was killed by pro-regime militiamen in the eastern city of Deir Ezzor. A 10-year-old girl died there of injuries sustained a day earlier, it added.
The security forces went into action on Thursday after mass demonstrations late on Wednesday in several districts of Homs, the Observatory said.
It said security forces also opened fire to disperse demonstrations in the country's second city of Aleppo, in the north.
The United Nations says that more than 2,200 people have been killed since the beginning of near-daily protests across the country against Assad's regime in mid-March.
Activists on their Facebook page Syrian Revolution 2011 defiantly called for fresh protests on Friday, the Muslim weekly day of prayers and rallying point for demonstrations.
The rallies will be held under the slogan of "death rather than humiliation," it said. "We are ready to die in the millions as martyrs."
In the YouTube video posted late on Wednesday, the attorney general of the flashpoint rebellious province of Hama, Mohammed Adnan al-Bakkour, announced his resignation.
He said he took the decision after hundreds of jailed peaceful demonstrators were killed by the authorities and buried in mass graves, and 10,000 were arrested arbitrarily.
But the official SANA news agency, which reported on Monday that Bakkour had been kidnapped en route to work with his driver and bodyguard, quoted officials as saying his statement had been made under duress.
Bakkour also cited the deaths of about 320 people under torture at Hama police stations, "the arbitrary arrest of about 10,000 people" and the demolition of homes by the army while occupants were still inside.
The United States denounced what it called the Syrian regime's "abhorrent abuse" of prisoners, following an Amnesty International report of 88 deaths in custody between April 1 and August 15, including 10 teenagers.
In at least 52 of the cases, Amnesty said "there is evidence that torture caused or contributed to the deaths," citing signs of violent beatings, burn marks and cuts.
Assad's regime has defied Western sanctions over its deadly crackdown on dissent, blaming "armed terrorist gangs" for the violence.
"Syria must be allowed to move forward," Clinton said on Thursday. "Those who have joined us in this call must now translate our rhetoric into concrete action to escalate the pressure on Assad and those around him."
This pressure must include "strong new sanctions targeting Syria's energy sector to deny the regime the revenues that fund its campaign of violence."
The European Union is to formally adopt a ban on Syrian oil imports on Friday, but the embargo will not take effect until November 15 for existing contracts after Italy insisted on a delay, according to diplomats in Brussels.
They told AFP that the EU would also expand its list of people targeted by an assets freeze and travel ban.