Lebanese protesters stormed the foreign ministry in Beirut on Saturday as anger exploded over a deadly blast that made hundreds of thousands homeless and shocked the world.

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.

As security forces fired tear gas to disperse strone-throwing demonstrators, Prime Minister Hassan Diab said he would seek early elections, saying it was the only way to “exit the country’s structural crisis”.

Demonstrators marched through streets ravaged by the blast, gathering in the central Martyrs’ Square, where a truck was on fire.

The police said an officer had fallen to his death after an “assault” by “a number of murderous rioters” during the protests.

“A member of the Internal Security Forces died while…. helping people trapped inside the Le Gray hotel” in downtown Beirut, the police force said on Twitter, without providing additional details.

That came after 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,” he said, appealing to the international community to boycott the government.

In an apparently coordinated strategy, others stormed the headquarters of the country’s banking association, a focal point of anger during recent mass protests over corruption and Lebanon’s collapsing economy.

They were later chased out by security forces who entered via a back door and doused the fire.

A group also briefly entered the economy ministry, scattering piles of documents in the street.

The Lebanese Red Cross said it had taken 63 people from the protest to nearby hospitals and treated another 175 at the scene, without specifying who they were.

As rescuers made last-ditch attempts to find survivors amid the rubble, efforts were afoot to drum up international support for the disaster-hit country ahead of a virtual aid conference on Sunday.