Protests against the Lebanese government turned violent for a second day on Sunday, and Prime Minister Tammam Salam threatened to resign as public discontent brought thousands into the streets.

Anger at the Salam-led unity cabinet grouping Lebanon's fractious politicians has come to a head over its failure to resolve a crisis over garbage disposal that reflects the wider failings of the weak state.

Salam's cabinet has been hamstrung by political and sectarian rivalries that have been exacerbated by wider crises in the Middle East, including the war in neighboring Syria.

Salam, in a televised address, warned that Lebanon was headed towards collapse and that a bigger problem than the trash crisis was the country's "political garbage".

Thousands of protesters have taken to the streets of Beirut this weekend as part of the "You Stink" campaign directed at the government.

Water cannon and tear gas were fired at protesters, and demonstrators threw rocks and sticks at riot police as violence flared near Salam's offices in central Beirut. "The people want the downfall of the regime," chanted protesters.

Security forces fired into the air, and clouds of tear gas wafted through the streets as police tried to force protesters from the area.

Some demonstrators lit fires. A tree next to a church was set ablaze, road signs were pulled from the ground, and shop fronts smashed. Violence also flared on Saturday night.

Many dozens of people have been hurt over the two days. Thirty members of the Internal Security Forces were injured on Sunday, one seriously, the National News Agency said.

A leader in the You Stink campaign said "infiltrators" were behind the violence. "We started peacefully, and we will continue peacefully," Hassan Shams told New TV.

Samer Abdullah, a 39-year-old activist, said: "People went out because they don't have power or electricity. They have a million problems, and the garbage problem is the tipping point."

There was no obvious participation by any of the big, mostly sectarian parties that have long dominated Lebanese politics.