Beirut - Lebanese troops deployed in Sunni areas of the capital as more sectarian violence erupted, stoking fresh fears after a top security official was killed in a bombing blamed on neighbouring Syria.
The army said it was determined to restore order, but the northern port of Tripoli was also shaken on Monday by fighting between partisans and opponents of Syrian President Bashar Assad that killed seven people.
On Monday afternoon personnel carriers entered Beirut's Sunni district of Tariq Jdideh, which had been a hotspot all day. Soldiers took up position on streets leading into the district to keep them open, a military spokesperson said.
Six people were wounded when the army made a pre-dawn sweep of Tariq Jdideh in pursuit of armed men, and automatic weapons and anti-tank rocket fire could be heard.
Later, soldiers responded after being fired on as they tried to clear a road into the district, a stronghold of opposition leader Saad Hariri. His supporters had blocked it despite calls by the former premier to stay off the streets.
The army spokesperson said a 20-year-old Palestinian, Ahmad Quaider, was shot after firing at an army patrol.
In Tripoli, a Sunni bastion where opposition to Assad is strong, seven people were killed and 12 wounded during clashes between Sunnis and Alawites, an offshoot of Shiite Islam to which the Syrian president belongs, security sources said.
Two Alawites and five Sunnis died.
The same sources reported snipers in the city late on Monday.
Most powerful military force
Clashes have erupted regularly in Tripoli as tensions spill over the border from Syria, where a 19-month-old anti-regime revolt has left more than 34 000 people dead.
Lebanon has been on edge since Friday, when police intelligence chief General Wissam al-Hassan died in the Beirut bombing.
The attack sparked immediate calls for Prime Minister Najib Mikati, whose cabinet is dominated by Syrian ally Hezbollah, to resign.
Hezbollah's militia, which never disarmed after the 1975-90 civil war, is the most powerful military force in Lebanon.
A statement from the army high command said it was "committed to its role of stopping security breaches and maintaining civil order".
The statement acknowledged that the country was "going through a critical time," but said the army would act to prevent the assassination of Hassan being exploited as an opportunity to murder the nation as a whole".
Lebanon is a multi-faith country in which Christians, Shiite and Sunni Muslims each make up about one-third of the population.
Under a complex but unwritten arrangement, the president must be a Maronite Christian, the premier a Sunni and the speaker of parliament a Shiite.
Sunnis are furious over what they call the Syrian assassination of Hassan, also a Sunni, who was noted for pursuing alleged Syrian crimes in Lebanon including the 2005 assassination of Hariri's father, Rafiq.
Sunday's funeral for Hassan, who was intelligence chief of the Internal Security Forces, had been billed as an opportunity to protest against Syrian meddling in Lebanon. But the mood quickly turned to fury at Mikati.
After former premier Fuad Siniora, speaking at the funeral, joined calls for Mikati to resign, a few hundred young men tried to storm the Serail, the seat of government. Police drove them back by firing in the air and using tear gas.
Mikati said on Saturday he would stay, at President Michel Sleiman's request, to avoid a "political vacuum" in the volatile country.
Later, Hariri appealed to his supporters "to stay off the streets, because we want to oust this government by peaceful and democratic means".
Lebanese university professor Ghassan al-Azzi said Hariri is focusing his political fire on Mikati, rather than taking on Hezbollah head on, because "if you take Hezbollah on directly, it means without a doubt that you are in favour of civil war".
Clashes between Sunni and Shiite gunmen in Beirut in 2008 brought Lebanon close to a new civil war and there are fears it will be further destabilised by the conflict in Syria.
The envoys to Beirut of the UN Security Council's permanent members met Sleiman and called for national unity.
US officials said on Monday they would send a team from the Federal Bureau of Investigation to help Lebanon investigate the Beirut car bombing.
Secretary of State Hillary Clinton stressed Washington's support for Lebanon's sovereignty, in a phone call with Mikati.