Thousands of Lebanese demonstrators have blocked major roads in and around the capital Beirut at the start of a general strike.

Smoke billowed over the city as protesters burned tyres and piled up stones to block the roads and prevent anyone from going to work.

The Hezbollah-led opposition called the action as part of a continuing campaign to force the government to resign.

The authorities have warned troops might be used to maintain order.

Protesters turned out early on Tuesday to cut off several streets in central Beirut, witnesses said.

The only road leading to Beirut's international airport was blocked, and several flights were cancelled as a result. Several main roads connecting the capital with other towns were also occupied.