Government forces and militia members loyal to Syrian President Bashar al-Assad have stormed the coastal village of al-Baida, killing between 50 and 100 people including women and children, Syrian opposition activists say.
The UK-based Syrian Observatory for Human Rights (SOHR) said on Thursday that the death toll would increase and could reach more than 100, with many of those killed appearing to have been "summarily executed" by shooting or stabbing.
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There were reports that the raid came in response to rebels attacking a busload of pro-Assad fighters, known as shabiha, earlier in the day, killing at least six and wounding up to 20 more.
Due to reporting restrictions in Syria, Al Jazeera cannot independently verify reports of violence.
Syria's official SANA news agency said troops killed "terrorists", the regime term for the rebel fighters, and seized arms.
The SOHR said the fighting was "the first of its kind in the Baniyas area", since the uprising began and that the army had cut off all communications with al-Baida.
Government troops appear to have made substantial gains in recent weeks, seizing several suburbs outside Damascus and recapturing territory in Homs province, birthplace of the armed uprising.
The report of violence in al-Baida came as Chuck Hagel, US defence secretary, said arming the Syrian rebels was now a possibility.
At a news conference on Thursday with his British counterpart, Philip Hammond, Hagel was asked if the US government was rethinking its opposition to arming the rebels and replied: "Yes."
Hagel said no decision had been reached and declined to say if he favoured arming the opposition.
"I'm in favour of exploring options and seeing what is the best option in coordination with our international partners," he said.
Meanwhile, UN chief Ban Ki-moon and ambassadors from the United States, Britain, France, Russia and China discussed on Thursday "possible diplomatic moves to end" the Syria conflict after UN diplomats said mediator Lakhdar Brahimi was determined to quit.
Diplomats, speaking on condition of anonymity, have said Brahimi wanted to resign from the joint UN-Arab League role because he is frustrated with international deadlock over how to end Syria's two-year civil war, which has killed 70,000.
"Brahimi is resigning, but I can't tell you which date," a senior Security Council diplomat said on condition of anonymity.
He said Ban was now being urged to become more personally involved in solving the crisis.
Some diplomats said Brahimi could step down by the end of May.
UN diplomats have also floated the idea of a "Geneva 2" summit to revisit an agreement by world powers in Geneva in June last year that said a transitional government should be formed in Syria "on the basis of mutual consent."
Brahimi, appointed last year after former UN Secretary-General Kofi Annan resigned as Syria mediator, also wants to distance himself from the Arab League, envoys said, because of its decision to recognise Syria's opposition.
Brahimi felt that move undermined his neutrality.