The Gangs of Beirut.(World Affairs)(Sunni, Shiite)

Byline: Mitchell Prothero

An eruption of street fights between Shiite and Sunni youths has many fearing a slide toward war.

When the scooter flies around the corner for the third time, Mazen and his friends--clustered outside a south Beirut phone shop--stop joking and glare at the interlopers. The riders stare back hard, then are gone.

"Amal Movement," says Mazen, describing the riders as followers of the militant Shiite party allied with Hizbullah. "They're from the neighborhood, so it's no problem. It's the Amal guys from outside we have to watch for."

Mazen and his friends, all in their 20s, are Sunni Muslims loyal to the government of Prime Minister Fuad Siniora. They're also linked to the Future Movement: Lebanon's dominant Sunni political party, which was founded by the slain former prime minister Rafiq Hariri and is now led by his son Saad. With the movement's blessing, Mazen and his buddies now spend every night protecting their neighborhood from Shiite gangs they accuse of repeatedly attacking them. Similar clashes have begun erupting regularly across Beirut--there have been more than a dozen this year. The violence has many fearing a return to the civil war that ravaged Lebanon between 1975 and 1990.

The last war largely pitted united Muslims against Lebanon's dominant Christian majority. The present conflict, by contrast, is pitting Sunni, Druse and Christian supporters of the Western-backed government against a mostly Shiite coalition led by Hizbullah. The split is being played out in Parliament, which has been unable to elect a new president since November. And it's playing out in the streets, where Sunni and Shiite toughs duke it out.

The geography of the battle has also changed too. During the civil war, the Green Line split the city into a Christian east and Muslim west. Today the fault line separates the northern, predominantly Sunni part of the city from the poorer, mostly Shiite southern suburbs.