Romania's Prime Minister is to stand down after huge protests over a nightclub fire that killed more than 30 people.

The leader of the ruling Social Democratic Party said Victor Ponta would go later on Wednesday after discussions within the ruling coalition.

Some 20,000 people took to the streets of the capital Bucharest on Tuesday evening calling for Mr Ponta to quit.

They also demanded the resignation of Interior Minister Gabriel Oprea and the mayor of the district where the Colectiv nightclub was located.

They shouted "Shame on you!" and "Assassins!" and waved Romanian flags.

Anger has been growing for some time in Romania against the government, which many view as corrupt, and Friday's fire has added to the discontent.

President Klaus Iohannis, who has declared three days of national mourning, wrote on his Facebook page on Tuesday: "I understand what is being asked and what is expected".

"They are right, someone has to take political responsibility. The next step is for politicians, who cannot ignore this sentiment of revolt".

Witnesses said the fire broke out during a heavy metal concert in the club when a spark ignited foam panels covering a pillar.

Around 500 people, including teenagers as young as 14, ran for the only exit as the basement filled with smoke.

The number killed has risen from the initial figure of 27 to 32, with more deaths expected.

Around 130 people are still being treated in hospital, dozens of them in a serious or critical condition.

A police investigation is under way, including into possible homicide charges.