Clashes between troops and deserters killed 12 people on Thursday, activists said, as Western powers sought to pressure Syria over its crackdown on dissent that the UN says has cost more than 2,900 lives.
"Seven soldiers and five deserters or civilians were killed in the clashes in villages west of Jabal al-Zawiya," near the Turkish border, the Syrian Observatory for Human Rights said, adding that 32 people were wounded.
The Observatory and the Local Coordination Committees, an activist network opposed to the regime of President Bashar al-Assad, said soldiers and security forces raided the villages in Idlib province backed by tanks.
Four people died in similar clashes earlier in the week between Syrian troops and deserters -- who defected after refusing to fire on anti-regime protesters -- also near the Turkish border, rights activists said.
An army officer who has taken refuge in Turkey, Colonel Riad al-Asaad, claims to have established an opposition armed force called the "Syrian Free Army", but its strength and numbers are unknown.
Analysts warn that the unrest in Syria, which began in mid-March as peaceful protests against Assad's autocratic rule, is becoming increasingly armed in response to the relentless gunning down of protesters by security forces.
The United Nations said on Thursday it estimates the crackdown has killed more than 2,900 people since mid-March but warns that the figure could rise to take into account those reported missing.
"The total number of people killed since protests began in Syria now stands at more than 2,900," UN High Commissioner for Human Rights spokesman Rupert Colville said, a day before the rights body was due to discuss the crisis.
Pro-democracy activists called for fresh demonstrations on Friday under the banner: "The Syrian National Council is our representative, mine, yours and that of all Syrians."
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Security forces on Thursday carried out arrests in the region of Deir Ezzor and in the eastern town of Abu Kamal, detaining 29 people.
In the village of Dael, in the southern region of Daraa, more than 15,000 people at the funeral of a 17-year-old youth chanted slogans against Assad's regime and a Russia-China veto which blocked a UN resolution on Syria.
Syrian troops entered Lebanese territory on Thursday and shot dead a Syrian farmer living in a remote border area of the eastern Bekaa region, a Lebanese security official told AFP.
European nations attempted to push a resolution through the UN Security Council on Tuesday that had called for "targeted measures" if Assad pursued his clampdown, but it was vetoed by Russia and China.
Syria, which maintains that the regime's opponents are armed gangs and terrorists trying to sow chaos, hailed the vetoes as "historic".
But furious Western powers have vowed to pursue efforts to punish Assad's regime with US Secretary of State Hillary Clinton on Wednesday led a fresh wave of criticism, saying the people of Syria "will not forget" the vetoes.
Clinton accused the Security Council of having "abrogated its responsibility" by failing to push through the European draft resolution. "The Syrian people will not forget," she said.
Following the lost vote at the Security Council, the British, French and German foreign ministers all said new pressure would be put on the Syrian government.
The European Union is preparing to target a Syrian commercial bank and 29 Iranians accused of human rights violations in fresh sanctions to be announced in the coming days, EU diplomats in Brussels said on Thursday.