Demonstrators blocked roads with burning tyres following the killing of an activist from the opposition Amal movement, raising tensions in a country suffering a deep political crisis.

A second person was shot and 14 were wounded in ensuing violence, security sources said.

The protesters used blazing tyres to block several main roads, including the airport highway. Heavy gunfire was heard and gunmen were seen in nearby Shi'ite and Christian streets.

Amal then called on its followers to halt the protests, which spread after the activist was shot dead. The army had fired into the air, but it was not clear who had shot the Amal member.

"We have no link to this action. We call on people not to react. We call on them to pull out of the streets," senior Amal official Ali Hassan Khalil told Reuters.

The Amal movement is part of an opposition alliance that has been locked in a power struggle for more than a year with the Western-backed government of Prime Minister Fouad Siniora.

Arab foreign ministers were meeting in Cairo on Sunday to draw up plans to secure the election of a new Lebanese president. Lebanon has been without a president since November though the majority and the opposition have agreed on army commander General Michel Suleiman to fill the post.

Sunday's protest began in the Mar Makhaeil area of southern Beirut, where Amal activist Ali Hassan Hamza was killed.

Security sources said at least one soldier was wounded when the protesters threw stones at security forces who had tried to break up the initial protest.

Soldiers deployed in the area -- near the site of a shooting that triggered Lebanon's 1975-90 civil war.

The army is widely viewed as neutral in the political conflict -- the worst since the civil war -- and has played a policing role to contain tensions between supporters of the rival sides.

Labour unions held protests last week to demonstrate against high prices.

(Reporting by Laila Bassam; Writing by Tom Perry; Editing by Giles Elgood)