FRANKFURT: Frankfurt police on Thursday arrested climate activists who brought Germany’s busiest airport to a standstill by gluing themselves to the tarmac.

Traffic was halted for two hours during the busy summer holiday season before the first of the airport’s landing runways was able to operate again at 0502 GMT, said an airport spokesman.

Seven activists had managed to reach the runway where they glued themselves onto the tarmac, a police spokesman said. An eighth was still trying to get through the perimeter fence when he was detained.

Police were able to remove the activists from the airport’s restricted grounds by 0815 GMT. All eight were placed under provisional arrest.

Climate activist group “Letzte Generation” (Last Generation) claimed responsibility for the civil disobedience action.

Its members used pincers to cut openings in the wire fence before making their way “by foot, with bicycles and skateboards to different points around the runways”, the group said.

A photo circulated by the group depicted a protester sitting on the tarmac with an orange banner that read: “Oil kills”.

The group is pushing for a binding international accord that would lead to an end in oil, gas and coal use by 2030.

Transport Minister Volker Wissing condemned Thursday’s protests as “criminal”.

“The climate activists are apparently seeking to bring about maximum damage,” he told German media.

“The legislators must react with maximum severity,” he added, calling for prison terms of up to five years in jail for those who storm airports.

“Anyone who violently forces their way into airports, occupies runways and blocks airplanes is endangering human lives,” he said.

Thursday’s protest action came a day after similar operations across several European airports.

Activists from Letzte Generation disrupted traffic at Cologne-Bonn airport for several hours on Wednesday by gluing themselves on the tarmac.

Several climate protesters were also arrested at London’s Heathrow airport.

Some passengers caught up in the protests at Frankfurt voiced their frustration.

Australian couple Jen Jung, 32 and Sam Smith, 33, who were heading to Warsaw for a wedding said they had had to scramble to rebook after their flight was cancelled.

“We understand that you have a point of view and you want to help the environment,” said Smith. “The thing is, pushing your point across to the point where everyone is affected... it’s not always the best idea.”

Butcher Heiko Schoene, 56, voiced his dismay when after learning that his flight to Zurich, where he and his family had a connecting flight to the Dominican Republic, had been cancelled.

“Obviously the shock and anger is great... because we saved up all year for our vacation and were happy to be able to finally go on holiday,” he said.

But doctor Ruth Zeilen-Boehle, 69, found the protests “necessary because too little is being done for the climate”.

While her flight was not cancelled, even if she had been affected, “I would have accepted it”, she said.

The protest organisers are part of the A22 Network of groups committed to non-violent climate protests. It said it was planning to disrupt airports in several countries in the coming months.

Global aviation is responsible for around 2.5 percent of global carbon emissions, more than the annual carbon footprint of Brazil and France combined.

Last Generation is known for mounting eye-catching protests — from throwing mashed potatoes at paintings in museums to glueing themselves on busy roads.