Activists in Lebanon vowed Monday to press ahead with protests over a trash crisis that have become an outlet for deep-rooted, broad-based frustration over political stagnation, corruption, and crumbling infrastructure.

At a news conference in Beirut, organisers of the "You Stink" campaign called for a new protest on Saturday against Lebanon's "corrupt political class".

Prime Minister Tammam Salam called an "extraordinary" meeting of the fragmented cabinet for Tuesday morning to discuss the "catastrophic" issue of waste disposal.

In a rare example of non-partisan action, thousands of people massed in central Beirut at the weekend to demand not only an end to the rubbish problem, but also a political overhaul and even the government's resignation.

On both Saturday and Sunday, protests that began peacefully descended into violence, with security forces using tear gas and water cannons against demonstrators.

On Monday, "You Stink" organiser Marwan Maalouf said the campaign was now fighting for three causes: a resolution to the trash crisis, freedom of expression and police accountability.

"In the beginning, this was a battle over the trash issue... But now there is a general battle against the political class," he said.

Maalouf did not specify a location for Saturday's demonstration.

Earlier on Monday, security forces erected concrete blast walls at the weekend's protest sites.

- 'Heading towards collapse' -

Environment Minister Mohammad Mashnuq announced on Monday that six new companies would be responsible for waste management, but declined to say where the refuse would be dumped.

Most of the companies awarded contracts are believed to have ties to prominent Lebanese political figures.

Maalouf called the new contracts "theft of public money".

Lebanon's trash crisis began after the government failed to find a replacement for the country's largest landfill, which closed on July 17 and left trash piling up in and around Beirut.

But at the weekend's protests, the largest so far, demonstrators also said they were angry about decades of electricity and water outages, unemployment, political stagnation and corruption.

"People are on the streets because they feel that at every level there is no one there for them," said Maha Yahya, a senior associate at the Carnegie Middle East Centre think-tank.

"It's an alarm bell for all the political leadership," Yahya said.

The weekend demonstrations were a rare example of non-partisan action on a social issue.

While Lebanon's many politicians can reliably turn out large numbers of supporters on a given political issue, broad-based protests are less common.

Although the demonstrations began peacefully, violence broke out at nightfall, with mostly young, male protesters throwing water bottles, rocks and fireworks at security forces who responded with tear gas and water cannons.

Organisers blamed unaffiliated "troublemakers" and condemned the attacks on police.

On Sunday, the prime minister condemned violence against protesters and acknowledged their frustrations.

- Fear of 'chaos' -

Salam warned that his 18-month-old government would become irrelevant if it failed to take action to address the public's concerns.

"We're heading towards collapse if things continue as they are," he said.

Lebanon is no stranger to political instability -- it has been without a president for more than a year, and Salam's cabinet has been unable to take decisions for months because of political gridlock.

Parliament has extended its mandate twice since the last election in 2009.

The conflict in neighbouring Syria has brought instability and more than one million refugees, straining an already overwhelmed infrastructure.

In that context, calls for the government's resignation have divided even some protesters, who fear a political void.

"I'm not at all attached to this rotten regime, but if you bring it down, what would you have instead? A chaos that could destroy the country," said Fadia Kiwan, a political science professor at Lebanon Universite Saint Joseph.

She said the demonstrators would be better off demanding a proper solution to the trash crisis.

"Within these limits, these young people could... put new pressure on the government and the political class."

Yahya also said the collapse of the government could "open the door to a lot more chaos".

She said political leaders needed to put public interests above their own "for once".

"I don't know if they're able to do that."