Security forces killed more than 100 people across Syria on Friday, one of the deadliest days in the more-than-10-month uprising that appears to be developing into a civil war.
The dramatic surge in violence occurred as the United Nations Security Council prepared for a meeting to discuss the Syrian crisis.
Arab media reported that the Arab League and Western powers were working on a resolution to stop the bloodshed.
Russia, which along with China vetoed a resolution that threatened sanctions against Syria in October, said it would oppose any new resolution that calls for President Bashar Assad to step down.
Activists in Syria said security forces backed by tanks and mortars had launched operations in the central cities of Hama and Homs, as well as the northern rebel stronghold of Idlib.
Some 44 people were killed when soldiers stormed the neighborhood of Al Hamidiyeh in Hama, the site of a 1982 massacre by government forces sent in to crush an uprising by the Sunni Muslim majority against the Alawite minority rule of the al-Assad family.
"Tanks are attacking the city from four directions. They are firing their heavy machine guns randomly," activist Abu Omar told DPA by phone as bursts of automatic gun fire crackled in the background. He said bodies lay uncollected in the streets and hospitals were desperately in need of blood transfusions for the wounded.
The London-based Syrian Observatory for Human Rights said attacks by the rebel army killed 12 security forces - six in a car bomb in Idlib and another six in an ambush in the southern town of Daraa.
Homs activist Omar Homsi said 18 people were killed in the city, when Syrian security forces opened fire upon a crowd leaving the mosque after Friday prayer.
In Syria's second largest city of Aleppo, which has been relatively calm since the protests erupted in March, activists reported that nine people were killed when security forces fired at protesters. Activists in an area near the capital, Damascus, reported that Syrian forces killed 21 people.
UN High Commissioner for Human Rights Navi Pillay said on Thursday that the world body could no longer keep track of the death toll in Syria due to the escalating violence.
The Arab League is referring the Syrian crisis to the United Nations after a peace mission it sent to Syria last month failed to stop the violence and was accused of providing a political cover for the government to continue its crackdown.
Gulf countries withdrew their observers from Syria this week in protest at the government's failure to stop the violence.
The head of the Arab League mission said on Friday that violence had "escalated dramatically" over the last three days. "The current violence does not help to create conditions to pave the way for a dialogue," Sudanese General Mohamed al-Dabi said in a statement released by the Arab League.
A report by Al-Dabi at the end of his one-month mission was criticized by the Syrian opposition as favoring the government.
Russia clearly indicated on Friday that it was ready to block any UN Security Council resolution calling on al-Assad to leave power. "Any decision about the future resolution of the situation in Syria should be put into motion without conditions, and a demand that Syrian President Bashar Assad leave power is one such condition," said Deputy Foreign Minister Gennady Gatilov. "We cannot support such a resolution," he was quoted as saying by the Interfax news agency.
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