Climate activists have disrupted flights at Frankfurt and Oslo airports on the second day of coordinated “oil kills” protests across Europe and North America.

Demanding an end to fossil fuels by 2030, supporters of Letzte Generation (Last Generation) briefly suspended flights at Frankfurt airport on Thursday morning. The activists said they had cut a wire fence, entered on bicycles and skateboards and glued themselves to the tarmac.

In Oslo, protesters from Folk Mot Fossilmakta and Scientist Rebellion Norway caused large queues by blocking a check-in lane with a banner that read: “Fast track to phase out.”

“I would rather not be here today, but I can no longer stand and watch as our elected officials do too little, too slowly,” said Ina Nagler, a climate researcher who took part in the Oslo protest. “The science is clear: We must drastically reduce the use of fossil fuels during this decade.”

The protests, which seek to pressure governments to speed the shift to a clean economy, have hit airports during the start of the busy summer season. On Wednesday morning, activists disrupted travel plans at airports from Helsinki to Barcelona. Further airport protests are expected in the US and Canada on Thursday.

The protests drew swift criticism from authorities. The campaign group Oil Kills said police had arrested 37 of the 91 activists involved, with 14 still in custody.

“These actions are stupid, criminal and dangerous,” said the German interior minister, Nancy Faeser, in a post on X. “Those who block runways risk not only their own lives, but also endanger others and harm all travellers.”

Letzte Generation said in response that it was the government’s climate policy – which it says is too weak to meet its targets – that was “dangerous and criminal”.

European governments have cracked down on disruptive climate protests with policing and sentencing that some human rights experts have described as “terrifying”.

Last week, Roger Hallam, the co-founder of Extinction Rebellion, was sentenced to five years in jail for planning to block the M25 motorway that surrounds London. German police have used laws designed to fight organised crime to tap phones, raid homes, freeze bank accounts and place activists in preventive detention.

Faeser said: “These acts must be punished more severely. We have proposed more severe prison sentences.”

The activists are calling on governments of rich nations to work together to establish a legally binding treaty to stop extracting and burning oil, gas and coal by 2030, as well as supporting poorer countries in their transition.

Leading scientists have long since backed calls for a fossil fuel phase-out, though the pace of change demanded by the activists is faster than that in pathways laid out by the Intergovernmental Panel on Climate Change and International Energy Agency. The World Health Organization, alarmed by the vast loss of life that climate breakdown entails, has endorsed a fossil fuel nonproliferation treaty.

The activists have announced further airport protests for Saturday.

“Flying is the fastest way to fry the planet so it’s key to start by cutting pointless and unfair flights like private jets or short-haul flights,” said Inês Teles from the campaign group Stay Grounded, which supports the protests. “The actions today and yesterday, disrupting airports, should be a shock to the system that is driving us towards climate catastrophe.”