Lebanon's divided government appeared powerless Wednesday to address a growing protest campaign that began with frustration over rubbish collection and ballooned into anger at a stagnant and corrupt political class.

On Tuesday night, the situation turned briefly violent when police ejected several dozen protesters from the "You Stink" campaign who had occupied part of the environment ministry to press the minister to resign.

In a sign of the ongoing impotence of the political class, parliament failed Wednesday for the 28th time to elect a new president.

The post has been empty since May 2014, and the legislature is so politically divided that every attempt to fill the job has failed.

This paralysis has increasingly become the target of "You Stink," which is not only demanding that Environment Minister Mohamed Mashnuq step down, but also insisting on new parliamentary elections and accountability for violence against protesters.

On Wednesday, dozens were seen gathering to demonstrate near the prime minister's serail in central Beirut, which security forces had reinforced with a thick cement barrier.

The call to protest came from "We Want Accountability," another civil society group that is demanding an end to corruption.

Organiser Neemat Badraddine, who had taken part in the sit-in the previous day, pledged demonstrations would continue at public institutions "which are the property of the Lebanese people".

- 'No storm in teacup' -

"You Stink" activist Assaad Thebian said the campaign would continue after the environment ministry sit-in, which was broken up by police after eight hours.

"It seems that the government is persisting in ignoring the demands of the Lebanese people," he said.

"The leaders are in a state of political bankruptcy, incapable of taking any decision."

He said "You Stink" had "taken the movement up a notch" with the sit-in.

"We also forced the minister to stay in his office for eight hours, which is rare for him!"

On Wednesday afternoon, Interior Minister Nuhad Mashnuq sought to forestall any repeat actions.

"Any occupation, sit-in or damage to public institutions will be dealt with immediately according to the law and with force," he warned.

However, he acknowledged some officers had used excessive force at a protest on August 22.

"Two officers will be referred to the disciplinary court, and six will be given disciplinary punishments for acting impulsively without reverting to their superiors," he said.

But Badraddine, the activist, said "Mashnuq is the one responsible and he should be held accountable."

As-Safir newspaper said Tuesday's sit-in was a sign the protest movement had staying power.

"Beyond the debate on the principle of whether the sit-in was right or not, what is most important is that this uprising has proved it is no storm in a teacup," it wrote.

"You Stink" is expected to announce its next steps Wednesday night, and another protest group has already called a new demonstration.

- Government must 'face facts' -

Analysts said the campaign was putting significant pressure on the government.

"Now the government and the political class know that they're under scrutiny," said Sahar Atrache, a senior analyst at the International Crisis Group.

But she said the movement risked petering out if it did not focus on achievable demands that would avoid polarising public opinion.

"People won't stay in the streets forever. If this movement one week after another is not really able to come up with clear objectives and concrete achievements, it's going to taper off with time."

She said the movement had garnered broad-based support by focusing on issues like power cuts and crumbling infrastructure, which cut across Lebanon's sectarian and political divides.

By targeting individual politicians, it risks falling "into the trap of divisive issues and polarisation," Atrache warned.

Lebanon's political class is broadly divided between two main blocs, each backed by different outside powers, and the tensions between them have been exacerbated by the war in neighbouring Syria.

Maha Yahya, a senior associate at the Carnegie Middle East Centre think-tank, said Lebanon's government should respond quickly to the protests.

"It needs to take seriously that this is not only about garbage, it's about governance," she told AFP.

"There are ways that they can move quickly on the environmental portfolio issue -- like with clear transparent bids (for trash collection)."

But she questioned whether the government was taking the activists seriously.

"They simply don't want to face the facts that this is a genuine movement of people who have had enough."