BEIRUT, LEBANON - Armed clashes in the Lebanese capital Wednesday between supporters of the Western-backed government and the Hezbollah-led opposition threatened this divided country's fragile calm.

The fighting began with opponents of the government setting tires ablaze to block the capital's main roads, notably those leading to the international airport where flights were suspended.

Protesters said they were answering a call by labor unions to oppose government policies aimed at combating inflation, but the unions in the end canceled a planned march because of the chaos.

Tensions quickly took on a political and sectarian character, with Sunni Muslim backers of the government and Shiite Muslim opposition supporters amassing in their respective neighborhoods and hurling stones at each other.

In mixed Shiite-Sunni districts, heavy gunfire erupted, and young men on each side hurled epithets and stones at each other. "God is with the Sunnis," shouted government supporters. "The Shiite blood is boiling," responded Hezbollah followers from across the street. Lebanese troops stood between them.

"It is going to get ugly and to be long," said Antoine Madi, 47, as he and neighbors watched plumes of smoke billowing from nearby neighborhoods.

There were no reported deaths but as many as a dozen injuries.

Shiite opposition supporters remained on the streets after sunset, indicating the protest will likely continue at least until Hezbollah leader Hassan Nasrallah speaks at a news conference today.

The latest surge of chaos in Lebanon's long political crisis began when pro-government politicians accused Hezbollah of spying on the airport to prepare for attacks and assassinations as well as for establishing a private telecommunications system. The Cabinet decided to remove the airport security chief, but he continued on the job.