Troops in Lebanon have begun a major security operation to force gunmen off the streets, trying to contain the violence prompted by the murder of a top intelligence official.
Syria has been blamed for the killing of General Wissam al-Hassan in a Beirut car bomb on Friday. With Lebanon already tense and deeply divided over the civil war next door, the murder has threatened to drag the country back into the kind of sectarian strife that plagued it for decades - much of it linked to Syria.
Sporadic gunfire rang out in Beirut as soldiers backed by armoured personal carriers with heavy machine guns took up position on major roads and dismantled roadblocks. At times, troops exchanged gunfire with Sunni gunmen.
Gen. Al-Hassan was a Sunni who challenged Syria and its powerful Lebanese ally, the Shiite militant group Hezbollah. The uprising in Syria is dominated by the Sunni majority fighting Syrian president Bashar Assad, who like many who dominate his regime, is a member of the Alawite sect - an offshoot of Shiite Islam. Lebanon and Syria share similar sectarian divides that have fed tensions in both countries, increasingly.
Most of Lebanon's Sunnis have backed Syria's mainly Sunni rebels, while Lebanese Shiites tend to back Assad.
The assassination has imperilled Lebanon's fragile political balance. Many politicians blamed Syria for the killing and angry protesters tried to storm the government palace after al-Hassan's funeral.
Prime minister Najib Mikati, a Sunni, said when he took up his post last year, he intended to protect all Lebanese, particularly Sunnis.
"I was convinced that through this mission, I am protecting my country, my people and especially fellow members of my sect."
The prime minister of Lebanon is usually a Sunni according to a sectarian division of top posts in the state. Over the past year, pro-Syrian Hezbollah and its allies have come to dominate the government.
Overnight Sunni and Shiite gunmen clashed in two Beirut neighbourhoods and officials also reported heavy clashes in the northern city of Tripoli and towns between the capital Beirut and the southern city of Sidon.