Protests have been raging across Lebanon for days over proposed new taxes despite assurances by Prime Minister Saad Hariri that his government will work to solve the country's economic crisis.

On Friday, the protests devolved into violence in the capital Beirut that saw riot police in vehicles and on foot clashing with demonstrators.

Here are the five things you need to know about the biggest protests in Lebanon in years:

What is happening?

Spontaneous anti-government protests erupted late on Thursday in the wake of austerity measures and a slew of new taxes that included charges on WhatsApp calls.

The government reversed the tax on WhatsApp calls but the protests have spread to other parts of the country with demand for better living conditions and an end to endemic corruption.

Protesters also took to the streets in the eastern Bekaa Valley and Tripoli, Lebanon's second-largest city.

Riots were also reported in the Roumieh and Zahle prisons.

The protests, the largest since 2015 'You Stink' campaign, come as the most serious challenge to Hariri's national unity government which came to power less than a year ago.

What are people demanding?

Public anger surged after parliament passed an austerity budget in July, and on Thursday it flowed into the streets over plans to introduce a $0.20 tax on calls via messaging apps, widely used in Lebanon.

The government scrapped the proposal within hours, but demonstrations carried on into the night before security forces dispersed them on Friday.

Despite tens of billions of dollars spent since the 15-year-long civil war ended in 1990, Lebanon still has crumbling infrastructure, including daily electricity cuts, rubbish piles in the streets and often sporadic, limited water supplies from the state-owned water company.

The protesters are demanding a sweeping overhaul of Lebanon's political system, citing grievances ranging from austerity measures to poor infrastructure.

Has it been violent?

After Hariri's speech, clashes flared in central Beirut's Riyadh al-Solh Square between demonstrators and security personnel, who fired tear gas canisters to clear the plaza.

Riot police rounded up protesters. They used rubber bullets and tear gas to disperse demonstrators in Beirut's commercial district. Dozens of people were wounded and detained.

Lebanon's internal security apparatus said 52 police were injured on Friday and its forces arrested 70 people.

Two Syrian workers died after they were trapped in a shop that was set on fire by protesters in Beirut on Friday.

Some protesters, including men in black hoods, blocked roads, set tyres on fire and used iron bars to smash storefronts in Beirut's posh downtown district.

As fires blazed, some streets in the capital looked like a battlefield, strewn with rubber bullets, smashed up cars, broken glass and torn billboards. Firefighters struggled late into the night to douse the flames.

Who are the protesters?

In a country fractured along sectarian lines, the unusually wide geographic reach of the protests highlights the deepening anger.

Cutting across sectarian and religious lines, Lebanese have come out on to the streets, waving banners and chanting slogans urging Hariri's government to go.

The Middle East country is divided on sectarian lines, with each of the main sects holding a position in government - the president must be Maronite Christian, the prime minister a Sunni Muslim and the speaker of parliament a Shia Muslim and so on.

Lebanese have been suffering from dire economic conditions in the heavily indebted country and from tax increases, with anti-government protests erupting several times in recent months.

Reflecting the scale of public anger, rare demonstrations were reported in neighbourhoods dominated by powerful Shia movement Hezbollah, not used to the opposition in its own bastions.

In an unprecedented move, Shia protesters also attacked the offices of their deputies from the influential Hezbollah and Amal movements in southern Lebanon.

"We came to the streets because we can no longer bear this situation. This regime is totally corrupt," said Fadi Issa, 51, who marched with his son.

"They are all thieves, they come into the government to fill their pockets, not to serve the country."

Government response so far

Lebanon's prime minister has given his coalition partners a 72-hour ultimatum to back his reform agenda amid growing nationwide protests.

In a televised speech on Friday evening, Hariri said he understood their anger and was trying to push through change.

He called on his coalition partners to give a "clear, decisive and final response to convince me, the Lebanese people and the international community ... that everyone has decided on reforms, or I will have something else to say".

​He gave them a 72-hour deadline to do so, without directly threatening to resign.

President Michel Aoun received a delegation on Friday representing protesters.

Aoun's office posted a photo of the meeting that consisted of eight persons sitting with Aoun at the presidential palace in Beirut's southeastern suburb of Baabda.

A member of the delegation told reporters that they told Aoun the government must resign and be replaced by an emergency Cabinet that calls for early parliamentary elections.