The demonstrators blocked roads to Beirut's international airport with dirt and burning tyres, while thousands of soldiers and police deployed across the capital.
 
After the gun battles, ambulances were seen rushing to the scene. There was no immediate word on casualties.
 
Food crisis
 
James Bays, Al Jazeera's correspondent in Beirut, said he had heard a lot of gunfire.
 
He said the strike action comes as many Lebanese struggle to meet the rising cost of food.

"Lebanon has had a very bad harvest, which means that food prices are rising, making it very hard for the very poorest in society," he said.

"That is why the labour unions called for this protest to take place today."

Siniora has come under increasing pressure
from the Hezbollah-led opposition [AFP]
Pro-government political groups and labour unions called on people to ignore the strike, while the opposition called on people to join a demonstration in Beirut later on Wednesday.

Labour unions at Beirut airport were taking part in the one-day strike, announcing a six-hour work stoppage starting mid-morning.

The strike has so far been largely confined to Shia Muslim areas of Beirut and its southern suburbs, where Hezbollah has strong support.

But in central Beirut, opposition supporters burned tyres only a few blocks from the office of Fouad Siniora, Lebanon's prime minister.

Opposition supporters have held a sit-in political demonstration in downtown Beirut since December 2006, shortly after Hezbollah pulled its representatives out of Siniora's cabinet.

Government crackdown

The action comes a day after the Lebanese prosecutor-general declared that he intended to pursue people and institutions with Hezbollah's private telecommunications network.

The government says that the network is being used by Hezbollah for military purposes, calling it illegal and a threat to state security.

The Lebanese cabinet also decided to remove Beirut airport's security chief over alleged ties to Hezbollah.

That came after the ruling political bloc alleged that Hezbollah had stationed surveillance cameras close to the airport's runways.

Hezbollah and Shia political and religious leaders have rejected the government's allegations.

The Lebanese government says Hezbollah is trying to set up a state-within-a-state, while Hezbollah says the majority bloc in parliament is too close to the United States.

Hezbollah, which is supported by Syria and Iran, is listed as a terrorist group by the United States and Israel.

Lebanon has been without a president since November. The opposition has boycotted 17 parliamentary sessions to formally select a new president, citing problems with power sharing in the cabinet.