Lebanon's prime minister threatened to resign on Sunday, warning rival parties in his unity cabinet that the state faced collapse because of paralysis that has come to a head with its failure to resolve a crisis over rubbish disposal.

Protesters called for a second day of demonstrations against Prime Minister Tammam Salam's cabinet on Sunday after at least 35 people were injured on Saturday night when security forces used water cannons and tear gas to disperse several thousand demonstrators in central Beirut.

Salam's government has suffered almost complete paralysis since it took office last year as wider crises in the Middle East, including the war in neighbouring Syria, have exacerbated Lebanon's own political and sectarian divisions.

"I warn that we are going are going towards collapse if matters continue," Salam said in a televised address. "Frankly, I have not and will not be a partner in this collapse. Let all officials and political forces bear their responsibilities."

He described as excessive the force used against protesters on Saturday and said those responsible would be held to account.

On Sunday, several hundred protesters gathered near the government headquarters on Sunday chanting anti-government slogans. Activists called for a bigger protest later in the day.

Their campaign "You Stink" is a response to trash being left uncollected in and around Beirut last month when a refuse tip closed, with no agreement on an alternative. While collection has resumed, no solution has been found.

"Political Garbage"

The Salam government brings together rival Lebanese parties, including the Sunni-led Future Movement of Saad al-Hariri, Shi'ite Hezbollah, and competing Christian groups.

Should it collapse, Salam's government would stay on in the caretaker capacity. However, his resignation would trigger a constitutional crisis. In Lebanon, it is the president who appoints the prime minister, but the presidency has been vacant since last year.

Salam said that if a cabinet meeting scheduled for Thursday was not productive on issues including a tender to decide on a new refuse collection company, "there would be no necessity for the government after it".

"The trash is the straw that broke the camel's back, but the story is much bigger than this straw. It is the story of the political garbage in the country and the political trash in the country," Salam said.

He also warned the heavily indebted government would be unable to pay salaries next month. Unable to issue new debt, it risked being classified "among the failing states".

Lebanon's public debt currently stands at about 143 percent of gross domestic product, a government source said.

Lebanon, still rebuilding from its 1975-1990 civil war, has been repeatedly jolted by spillover from the Syria war, including political violence and a major refugee crisis.

Hezbollah, a powerful Iranian-backed party, is fighting alongside President Bashar al-Assad in the Syrian conflict.