Extinction Rebellion activists have thrown buckets of “blood” outside Downing Street to call for greater action on climate change. About 400 demonstrators, including families with children, spilled more than 200 litres of red paint to make the severity of climate change “viscerally clear”.

The blood was meant to symbolise “the death of our children” and the hellish future young people faced, the group said in a statement.

Paolo, 61, a translator, said: “We are here to mourn the loss of life, and for the life that has not yet been born; and to protest the injustice of this for future generations. I have no children of my own, but I haven’t stopped loving the world.”

Hector, aged 10, said: “Many animals will go extinct if we do not act now. We have invested all our support in the government. But in our time of need, they have deserted us. We need the press and the government to tell the truth.”

The protest follows a demonstration in Edinburgh on Friday, when police arrested 14 Extinction Rebellion activists who were protesting at an oil industry dinner at the National Museum of Scotland in Edinburgh. About 30 people staged a sit-in at the museum before hundreds of oil company executives gathered for the annual dinner of the Scottish Oil Club.

The protesters hung two banners from the balcony of the museum’s main hall that read, “Climate emergency” and “Smash the patriarchy – save the planet”.

They were asked to leave by Police Scotland, but 13 protesters remained in the building, six of them joined together with bicycle locks. They were arrested and removed from the museum at about 8pm.

It is understood that the 14th activist was arrested at about midnight after unfurling a climate protest banner from the same balcony. An Extinction Rebellion spokeswoman said all 14 had been charged with breaching the peace.

It was the latest in a series of direct action protests and occupations by Extinction Rebellion activists in Scotland, including a sit-in at the Scottish parliament and a demonstration in Glasgow.

The campaign group said about 300 people staged a party on Chamber Street outside the museum before executives from oil firms including Shell, BP and Total arrived.

“When guests started arriving, protesters lined the entrance to the museum and sang, chanted and spoke to them about the climate emergency,” the group said, before criticising the museum for renting out its building for the event.

Extinction Rebellion, which has spread to a number of countries after being launched in London last year, argues that governments and industries are failing to address the climate crisis with sufficient urgency.

They believe the UK needs to rapidly cut carbon emissions, with the aim of no net carbon emissions by 2026, about 25 years earlier than its current target. They argue that the UK’s oil industry, which is based in Aberdeen, enjoys £10.5bn a year in subsidies and is continuing to develop new oilfields, despite evidence of increased manmade global warming.

Mim Black, an Extinction Rebellion Scotland spokeswoman, said: “Climate chaos is already under way across the planet and we know that the fossil fuel industry is a major driver of this. We must immediately start putting safety before profit.”

Police Scotland said its officers were deployed at 4.30pm on Friday. After the museum closed to the public, the protesters were asked to leave but refused. “Following a period of negotiation police provided a proportionate response to the protest and 13 people, a mix of men and women, have been arrested,” the force said.