"We are staying here. We call on the Lebanese people to occupy all the ministries," a demonstrator said by megaphone.
About 10,000 people gathered in Martyrs' Square, some throwing stones. Police fired tear gas when some protesters tried to break through the barrier blocking a street leading to parliament, a Reuters journalist said.
Police confirmed shots and rubber bullets had been fired. It was not immediately clear who fired the shots.
The protesters said their politicians should be hanged and punished over their negligence which they say led to Tuesday’s gigantic explosion that killed 158 people and wounded more than 6,000.
The protesters chanted "the people want the fall of the regime", a popular chant during the Arab Spring uprisings of 2011. "Revolution. Revolution." They held posters saying "Leave, you are all killers". “Leave you Rubbish”.
Prime Minister Hassan Diab said the only way out was early parliamentary elections.
The protests were the biggest since October when thousands of people took to the streets in protest against the ruling elite's corruption, bad governance and mismanagement.
“You have no conscience, you have no morality. Go home! Leave! Resign, Enough is enough,” shouted one of the protesters. “What else do you want You brought us poverty, death and destruction,” said another.
"Resign or hang," said one banner.
Soldiers in vehicles mounted with machine guns patrolled the area amid the clashes. Ambulances rushed to the scene. One teenager fainted after being overcome by tear gas.
"Really the army is here Are you here to shoot us Join us and we can fight the government together," a woman yelled.
Tuesday's blast was the biggest in Beirut's history. Twenty-one people were still reported as missing from the explosion which destroyed a large swathe of the city and caused collective losses estimated at $15 billion.
The government has promised to hold those responsible to account. But few Lebanese are convinced. Some set up nooses on wooden frames as a warning to Lebanese leaders.
The prime minister and presidency have said 2,750 tonnes of highly explosive ammonium nitrate, which is used in making fertilisers and bombs, had been stored for six years without safety measures at the port warehouse.
The explosion hit a city still scarred by civil war and reeling from an economic meltdown and a surge in coronavirus infections. The blast rattled buildings on the Mediterranean island of Cyprus, about 100 miles (160 km) away.
For many, the blast was a dreadful reminder of the 1975-1990 civil war that tore the nation apart and destroyed swathes of Beirut, much of which had since been rebuilt.
Some residents, struggling to clean up shattered homes, complain the government has let them down again.
"We have no trust in our government," said university student Celine Dibo as she scrubbed blood off the walls of her shattered apartment building. "I wish the United Nations would take over Lebanon."
Many people denounced their leaders, saying none of them visited the site of the blast to comfort them or assess the damage while French President Emmanuel Macron flew from Paris and went straight to the scene to pay his tribute.
Lebanon's Kataeb Party, a Christian group that opposes the government backed by the Iran-aligned Hezbollah, announced on Saturday the resignation of its three lawmakers from parliament.
Macron, who visited Beirut on Thursday, promised aid to rebuild the city would not fall into "corrupt hands". He will host a donor conference for Lebanon via video-link on Sunday, his office said. U.S. President Donald Trump said that he will join. urn:newsml:reuters.com:*:nL1N2FA032 Aoun said on Friday an investigation would examine whether it was caused by a bomb or other external interference. Aoun said the investigation would also weigh if the blast was due to negligence or an accident. Twenty people had been detained so far, he added. urn:newsml:reuters.com:*:nL8N2F93XS
'WE CAN'T AFFORD TO REBUILD'
Some residents wondered how they would ever rebuild their lives.
Tearing up, Bilal Hassan used his bare hands to try to remove debris from his home. He has been sleeping on a dusty couch besides pieces of splintered glass.
When his three wounded teenage children ran for their lives they left blood stains on the staircase and walls.
"There is really nothing we can do. We can't afford to rebuild and no one is helping us," he said, standing beside a large teddy bear that was blown across his home, and a damaged photograph of him and his wife.
Bulldozers ploughed through the wreckage of mangled homes and long rows of flattened cars as soldiers stood by. Volunteers with shovels streamed through streets.
Danielle Chemaly said her charity organisation, whose headquarters was destroyed, had provided assistance to 70 families who were left homeless.
"We don't know what we can do for families in the future," she said.
Officials have said the blast could have caused losses amounting to $15 billion. That is a bill that Lebanon cannot pay after already defaulting on a mountain of debt - exceeding 150% of economic output - and with talks stalled on an IMF lifeline.
For ordinary Lebanese, the scale of destruction is overwhelming. Marita Abou Jawda was handing out bread and cheese to victims of the blast.
"Macron offered to help and our government has not done anything. It has always been like that," she said. "After Macron visited I played the French national anthem all day in my car."
(Additional reporting by Maher Chmaytelli, Laila Bassam, Suleiman Al-Khalidi, Ezgi Erkoyun, Ellen Francis and Richard Lough Editing by Frances Kerry and Nick Macfie) ((email@example.com; +971 52 503 5332; Reuters Messaging: firstname.lastname@example.org))