Syria says authorities have seized a cache of weapons smuggled into the country from neighboring Turkey.

The state-run SANA news agency said Monday the weapons included more than 150 shotguns and Kalashnikov rifles, along with several rocket-propelled grenade launchers.

The report comes a day after SANA said gunmen in the troubled northwest killed the 21-year-old son of the country's top Sunni Muslim cleric in an ambush. The cleric, Grand Mufti Ahmad Badreddine Hassoun, is considered a close supporter of President Bashar al-Assad's government and has echoed its claims that Syria's unrest is the result of a foreign conspiracy.

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.

Syria's main opposition groups said Sunday they have 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.

A prominent secular dissident, Bourhan Ghalioun, announced the Syrian National Council's formation Sunday in the Turkish city of Istanbul. While he said the group rejects foreign intervention that “compromises Syria's sovereignty,” Ghalioun appealed to the international community to protect civilians from what he called a government “war” against them.

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.

Ghalioun was flanked in Istanbul Sunday by representatives of each group, which include members of the largest Syrian opposition factions. The SNC comprises a general assembly, a general secretariat and an executive committee whose members will chair the council on a rotating basis.

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.”