BERLIN >> Climate activists blocked flights at two German airports for several hours Thursday in protest against the most polluting form of transportation, and to demand tougher government action to reduce greenhouse gas emissions.

The group Last Generation said several of its members entered the grounds of Hamburg Airport around 6 a.m. (0400 GMT) and glued themselves to the runway on the first day of the school vacation in the north German city.

Dozens of flights were canceled and 10 arrivals had to be diverted to other airports, Germany’s dpa news agency reported.

Members of the group also cut through a security fence at Duesseldorf Airport in the west and blocked an access route to the runway, disrupting several flights before operations resumed.

In a statement, the group accused the German government of lacking a strategy to tackle the climate crisis and called for immediate measures to cut emissions in the transportation sector, including ending tax exemptions for airline kerosene.

Aviation is responsible for a significant share of global emissions. If the sector were a country, it would rank in the top 10 global emitters, according to the European Commission.

Senior German government officials slammed the protests and called for them to end.

“The Last Generation isn’t protecting the climate, they’re engaged in criminal activity,” said Transport Minister Volker Wissing, who has blocked several proposals for cutting emissions from road and air travel in recent years.

He and Justice Minister Marco Buschmann, both members of the Free Democratic Party, accused the activists of dividing society by preventing people from flying on “well-earned holidays.”

Last Generation insists its protests are peaceful, albeit disruptive, though motorists facing delays when the group blocks roads have at times attacked the activists.

German prosecutors raided the homes of several of the group’s members in May on suspicion of forming or supporting a criminal organization.