Dozens of people were wounded in overnight clashes between security forces and supporters of Lebanon's Hizbullah and Amal parties, the civil defence said on Tuesday (December 17th).
It was the latest incident of violence in what have been largely peaceful protests since October 17th against a political class deemed inept and corrupt.
The street movement pushed the prime minister to step down on October 29th, but the country's bitterly divided political parties have failed to agree on a successor.
Shortly before midnight on Monday, young supporters of Hizbullah and Amal tried to attack the main anti-government protest camp in central Beirut.
The angry young men arrived on foot and scooters, apparently fired up by a video shared online that they deemed offensive to Shias.
They lobbed stones and fireworks towards the anti-riot police trying to prevent them from entering the largely empty main square.
The attackers also torched several cars. The security forces responded with teargas and a water cannon.
Civil defence said 23 people were taken to hospital, while 43 were treated at the scene. It was not immediately clear from which side the wounded were.
In the southern city of Sidon, young protestors also attacked a protest camp during the night, destroying several tents.
This was not the first time Hizbullah supporters attacked the peaceful protestors in Lebanon.
On Tuesday (October 29th), a group of Hizbullah supporters assaulted a protest site on Beirut's Ring Bridge, attacking the demonstrators with sticks, beating them, and throwing stones at them, before going on to storm Martyrs' and Riad al-Solh squares, where they destroyed tents and set them on fire.
Lebanese academic Imad Salamey said the Monday night clashes could have been an attempt to undermine the protests.
"Stirring sectarian strife is one of the ways used by those in power to divide Lebanese and weaken the street movement," he said.
But "the economic crisis today reflects a complete regime crisis that cannot be solved or faced with sectarian movements", warned the professor at the Lebanese American University.
Lebanon's economy is sliding towards collapse, after years of political deadlock compounded by the outbreak of civil war in neighbouring Syria in 2011.
The World Bank projects it will contract by more than 0.2% this year. It has warned that poverty could shoot up from a third to half the population if the deadlock is not resolved.
Salamey said solidarity between Lebanese has only increased "after people started losing their jobs and companies and being unable to withdraw money from the banks".
"The economic crisis has broken the barrier of fear, or at least the barriers between different religious sects," he said.
The international community has urged Lebanon to speed up the formation of a new government to implement economic reforms necessary to unlock billions of dollars in foreign aid.