Explosions and gunfire rang out across the Lebanese capital Beirut as opposition supporters held a one-day general strike calling for higher pay.
Strikers set up barricades of burning tyres on key routes to the port, airport and Beirut's commercial centre.
The cause of the explosions was not clear, but reports say armed opposition and pro-government groups may have fired rocket-propelled grenades.
The country is witnessing its deepest
political crisis since the civil war.
Lebanon has been without a head of state for five months because of a power struggle between the Western and Saudi-backed government and the Hezbollah-led opposition which is supported by Syria and Iran.
Protestors burn tyres and cars in Lebanon
Pro-government supporters exchanged rifle and grenade fire with Hezbollah sympathisers in three neighbourhoods, security sources said.
There was no immediate word of casualties but ambulances where seen heading towards the areas.
Earlier in the day a stun grenade was detonated in a crowd in West Beirut, causing minor injuries. It was not known who threw the grenade.
The BBC's Jim Muir in Beirut says although this is ostensibly a workers' strike, it was a highly politicised affair reflecting the acute polarisation and tension between the government and opposition.
Protesters say wages have not kept up with fuel and food prices
Labour unions cancelled Wednesday's main event - a march through Beirut - a few hours before it was scheduled to take place, because of conditions along the route.
Tensions rose on Tuesday after the government announced it would shut down Hezbollah's private telecommunications network.
The head of airport security was also dismissed amid allegations he had allowed Hezbollah to set up spy cameras at the airport; Hezbollah strongly denied the claim.
Unions are demanding that the government triple the minimum monthly wage, which currently stands at $200.
Prices have been rising in Lebanon, especially food and fuel, with the situation exacerbated by the weakening of the US dollar, but Finance Minister Jihad Azour has warned that big pay rises would lead to rampant inflation.
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