The U.N. Security Council may vote Tuesday on a resolution condemning Syria's brutal crackdown against civilians, amid reports that security forces have carried out mass detentions in the rebellious central town of Rastan.

Diplomats say it remains unclear whether Russia will veto the resolution or abstain from voting.

Moscow opposes the imposition of sanctions against President Bashar al-Assad's government. The European-drafted resolution threatens “targeted measures” against Syria if it does not halt its military assault on pro-democracy protesters.

In Syria, activists say security forces in and around Rastan have arrested up to 3,000 people over the past three days in an effort to track down military defectors. Syria's official SANA news agency puts the number of arrests “in the dozens.”

For about a week, tank- and helicopter-backed troops battled insurgents and army deserters in Rastan. Syria's official news agency said Saturday that government forces have regained control of the town.

The military is reported to have deployed more forces in the town of Talbiseh, near Homs – another area that has defied government authority for months.

The Syrian military said Monday it has confiscated a cache of weapons and explosives smuggled into the country from neighboring Turkey. The seizure is said to include more than 150 shotguns and Kalashnikov rifles, along with several rocket-propelled grenade launchers.

Since the uprising began in March, the Syrian government has cast the opposition as an armed insurgency driven by Islamist militants – a description most other accounts have dismissed as a vast exaggeration.

Syria has been using military force to crush almost seven months of largely peaceful opposition protests demanding an end to Mr. Assad's 11-year autocratic rule.

On Sunday, gunmen in Syria's troubled northwest killed the 21-year-old son of the country's top Sunni Muslim cleric in an ambush. The cleric is considered a close supporter of Mr. Assad and has echoed its claims that Syria's unrest is the result of a foreign conspiracy.

In the Turkish city of Istanbul Sunday, Syria's main opposition groups joined to create a broad-based national council aimed at unifying their efforts to overthrow Mr. Assad's government, which they accuse of pushing the country to the brink of civil war.

The Syrian opposition consists of a variety of groups with differing ideologies. The newly formed council includes Syria's pro-democracy Damascus Declaration, the banned Muslim Brotherhood, various Christian and Kurdish factions and the grass-roots Local Coordination Committees, which have led nationwide street protests.

The United Nations says at least 2,700 people have been killed in the crackdown. The Syrian government says the dead include hundreds of security personnel killed by what it calls “armed terrorist groups.”