Police on Thursday arrested climate activists who glued themselves to the tarmac at Frankfurt airport, Germany's busiest, compelling it to temporarily suspend arrivals and departures.
Traffic was halted during the busy summer holiday season for two hours before the first of the airport's landing runways was able to operate again at 5:02 a.m. GMT, said a spokesperson at the airport.
Passengers were advised to check the status of their flights while the airport ramped up its operations again.
Seven of the activists had managed to reach the runway, where they glued themselves onto the tarmac, a police spokesperson said. The eighth was still trying to get through the perimeter fence when he was detained.
The spokesperson added that the police operation to clear activists off the airport's restricted grounds was ongoing. All eight were arrested.
According to the climate activist group "Letzte Generation" (Last Generation), which claimed the civil disobedience action, its members had 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."
A photo circulated by the group depicted a protester sitting on the tarmac with an orange banner that said, "Oil kills."
The group is pushing for a binding international accord that would end oil, gas and coal use by 2030.
Transport Minister Volker Wissing condemned the protests Thursday as "criminal" action and demanded tough penalties against the activists.
"The climate activists are apparently seeking to bring about maximum damage. The legislators must react with maximum severity," he told German media, 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.
The protest organizers are part of the A22 Network, a network of groups committed to nonviolent climate protests. The group said it was planning to disrupt airports in several countries in the coming months.
Protests were planned in Britain, Austria, the Netherlands, Switzerland, Canada, the United States and Norway, and U.K.-based activists from the alliance told Agence France Presse (AFP) earlier in July.
Global aviation is responsible for around 2.5% of global carbon emissions, more than the annual carbon footprint of Brazil and France combined.
The Last Generation is known for mounting eye-catching protests, from throwing mashed potatoes at paintings in museums to gluing themselves on busy roads.
Their tactics, which have proved deeply divisive, have led to some of their members being convicted.
"Instead of seeking tougher sentences, politicians should seriously take the scale of the disaster that they are themselves fueling," said Lisa Johnson, spokesperson of the group.
"Prison sentences won't shield us from heat waves, droughts, floods and dramatically rising sea levels," she warned.
Letzte Generation has said it will hold protests starting Sept. 25 against planned government subsidies for Kassel-Calden airport.
