BEIRUT, Lebanon — Armed clashes in the Lebanese capital yesterday 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 a political and confessional 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. Armed fighters belonging to the Hezbollah-aligned Amal movement and the pro-government Future Movement stood on the corners of empty streets.

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

Lebanon’s sectarian and political tensions mirror a broader regional conflict. America and Saudi Arabia support the Sunni-led government while Iran and Syria back the Shiite-led opposition.

Lebanon has been without a president since November amid an ongoing political deadlock between the two rival camps.

The latest upsurge of chaos in Lebanon’s ongoing 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 chief.

Hezbollah warned the government against laying hands on the group’s communications network, equating it to the weapons it stockpiles to take on Israel. The group’s supporters warned they would continue what in effect is a shutdown of the airport, a key transport conduit for a country that has hostile relations with one neighbors, Israel, and strained relations with another, Syria.

The main road linking the heart of the capital to the airport was blockaded with piles of sand and burned tires while hundreds of rioters roamed around on scooters. Television news channels showed footage of trucks dumping heaps of sand in the middle of the roads and protestors setting garbage containers and cars on fire to block traffic.

Lebanese officials have counted on the relatively nonpolitical army to maintain security. Yesterday, Lebanese soldiers backed by tanks stood by to prevent the clashes from escalating.

Most of the Sunni and Shiite parts of Beirut were closed and empty of passers-by.