Following similar actions last month, climate activists in Germany briefly disrupted traffic at the Munich airport on Thursday to protest the impact of air travel as "the ultimate climate killer."
Members of the group Letzte Generation, or Last Generation, said some of its members had glued themselves to the tarmac there, and that others had entered the grounds of the Berlin airport.
While a spokesperson for the Munich airport confirmed to The Associated Press that the northern runway had briefly been closed and the rerouting of planes had caused short delays, a spokesperson for the Berlin airport said that a police operation was ongoing but that air traffic had not been affected.
Photos showed police officers attempting to remove some of the activists from the roads and pictures posted to the activists' Twitter account later showed members holding signs blocking city streets.
Last Generation said in a statement that local law enforcement had been informed of the protest shortly before entering the premises.
"We are always ready for constructive talks, as we did yesterday with the Bavarian Minister of the Interior. But what we need in the face of the looming climate hell are actions and not just empty words," spokesperson Aimée van Baalen said.
The group also said that four members were in prison in Bavaria and had been "taken into preventive detention without trial."
In November, Last Generation staged a similar protest at the Berlin Brandenberg Airport and approximately 13 flights were forced to change their route or divert course.
Earlier in the year, climate protesters targeted famous works of art, poured onto freeways to stop traffic and poured out milk onto the floors of stores to fight for environmental justice.
Fox News' Timothy Nerozzi and The Associated Press contributed to this report.