Police and a protest group calling itself the Resistance Collective confirmed the early-morning incident at the airfield where Merz, a hobby pilot, parks his plane.

"The plan was to paint the aircraft pink to effectively take it out of service," the protest group said in a statement sent to AFP.

The activists carried a banner that read "Mobility for all, not just the super-rich!" and had also planned to leave behind a bicycle as a more climate-friendly means of transport for Merz, the group said.

Police said they foiled the plan after pulling over one of the activists near the Arnsberg-Menden Airport in Merz's native Sauerland region, about 40 kilometres (25 miles) east of the city of Dortmund.

The driver said he was looking for the local airfield, and police records showed the person had previously been "involved in politically motivated crime", according to a police statement.

Three other activists were then arrested for trespassing inside the airport's restricted area after police launched a subsequent search.

Police confirmed that Merz's personal aircraft was parked at the airport.

"We are acting in self-defence," one of the activists, Anja Windl, said in the group's statement.

"The climate catastrophe is escalating -- hunger, heat and natural disasters are claiming lives -- and yet Friedrich Merz is flying around in his own plane," Windl said.

"The chancellor, of all people, should be setting an example for the rest of us."

The three activists were caught on the tarmac of the small airport and are being held in police custody, according to the activists group.

Airports in Germany have repeatedly been targeted by climate protesters, who criticise the outsized emissions created by flights compared with other forms of transport.