BUCHAREST, ROMANIA—Romania’s government collapsed Wednesday after thousands of people took to the streets to protest a deadly fire at a heavy metal concert, the final straw after a five-month corruption investigation that has shaken the nation.

Prime Minister Victor Ponta said he and his government would resign “to take note of the legitimate grievances which exist in society,” adding: “I hope handing in my and my government’s mandate will satisfy the demands of protesters.” But thousands of people turned out for new protests Wednesday evening demanding early elections and more accountability in government.

Even before last weekend’s fire, the deadliest in Romania’s history, Ponta faced widespread calls to resign as he was tried on charges including tax evasion, money laundering, conflict of interest and making false statements. The charges relate to activities in 2007 and 2008, when he was a lawmaker and a lawyer. Ponta denies wrongdoing.

Then came the fire Friday night at the basement Colectiv nightclub, which sent panicked people stampeding for the single exit. The death toll stands at 32, with about 130 more hospitalized, dozens of them in serious or critical condition. The club’s three owners have been detained on manslaughter charges for allegedly failing to comply with fire regulations. Many Romanians also suspect authorities of taking bribes to overlook the violations.

After three days of mourning, some 20,000 people took to the streets Tuesday night in a spontaneous protest, shouting “Assassins!” and waving Romanian flags.

“It is not normal in a European Union country for our children to die like this,” said Mariana Draghici, a security guard who took part in the protest. “Something has to change in Romania.”

Ponta, who had resisted earlier calls from President Klaus Iohannis to resign, stepped down hours later but warned the collapse of his government could bring about instability.

“We have turbulence, uncertainty, and unrest,” he said. “We risk ruining everything we built.”

Iohannis said that if fire regulations had been respected “nobody would have died,” calling it a shame that so many had to die before the government caved into the pressure.

On Wednesday evening, thousands massed in Bucharest’s University Square and in at least three other cities, calling for early elections and better governance.

“I believe in a clean Romania, a dignified Romania, where citizens are respected,” said Alexandru Ispas, a 23-year-old history student.

Most likely, however, Ponta’s party will remain in place until parliamentary elections that aren’t scheduled until December 2016. Since the party dominates parliament, its leader will likely get the chance to form a government, and parliament will likely approve it. It’s only if parliament rejects the government twice that new elections would be called — an unlikely scenario.

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The protesters also criticized the powerful Romanian Orthodox Church, accusing it of failing to address an outpouring of national grief.

“We want hospitals, not cathedrals!” they chanted.

In a day of resignations, the mayor of the district where the nightclub is located stepped down, saying he felt morally guilty for the fire. The interior minister, who was already under fire over the death of a police motorcyclist who died in a crash while escorting his car, also resigned and said he would take no part in a future government.