A Lebanese policeman hits a demonstrator during clashes in Beirut on Saturday. AFP

Thousands of demonstrators, some of them brandishing nooses, had descended on the city centre to vent their fury at politicians they blame for Tuesday's explosion, which levelled Beirut port and killed 158 people.

Demonstrators marched through streets ravaged by the blast, gathering in the central Martyrs' Square as their grief gave way to rage.

A demonstrator breaks a shop window during clashes with security forces in Beirut. AFP

As security forces focused their attention on a tense demonstration a few hundred metres down the road, a group led by retired Lebanese army officers stormed the foreign ministry and declared it the "headquarters of the revolution".

"We are taking over the foreign ministry as a seat of the revolution," Sami Rammah, a retired officer, announced by loudspeaker from the ministry's front steps.

"We call on all the anguished Lebanese people to take to the streets to demand the prosecution of all the corrupt," appealing to the international community to boycott the government.

The health ministry said 158 people were confirmed to have died in the disaster, while at least 6,000 were wounded and 21 still missing.

The Netherlands announced that its ambassador's wife was among the dead.

Demonstrators chant slogans outside the premises of the foreign ministry in Beirut. Reuters

The blast has prompted an impressive aid response from both inside and outside Lebanon, but demonstrators' chants and the mock gallows they set up in the street made it clear that people want heads to roll.

But some of Lebanon's leaders seemed to consider the outpouring of international solidarity as an opportunity to break the government's diplomatic isolation.

Elsewhere, police fired tear gas to disperse groups of young men hurling stones and seeking to push towards parliament.

Two days after a landmark visit by French President Emmanuel Macron, activity was growing to drum up international support for the disaster-hit country ahead of a Sunday virtual aid conference.

For the fourth day running, Beirut woke to the sound of broken glass being swept on the streets, its inhabitants taking stock after one of the biggest blasts of its kind in recent history.

A fire at the port on Tuesday ignited a stock of ammonium nitrate, triggering an explosion that was felt as far away as Cyprus and destroyed entire neighbourhoods.

It was widely perceived as a direct consequence of corruption and incompetence, perhaps the most egregious case of callousness on the part of a ruling elite that was already reviled.

'Criminals'

"You were corrupt, now you are criminals," read one banner at the demonstration, while protesters chanted: "Revenge, until this regime reaches an end."

"We are hanging the nooses because the same people have been ruling us for 30 years," said Jad, a 25-year-old man working in advertising.

An injured demonstrator is evacuated during a protest in Beirut. Reuters

"They have robbed us of everything. We have nothing left: no dreams, no future... no dignity, no money, and now, no houses," said Rita, 33, whose home was gutted by the blast.

"We should not be forced to live this way," she said after reaching Martyrs' Square, a short walk from the blast site.

Despite high tensions, fuelled by resentment among the demonstrators that security forces had not been deployed to help the public in the aftermath of the blast, the protest passed off relatively peacefully.

Agence France-Presse