Greenpeace campaigners climbed a 40-metre billboard advertisement for Hyundai Motor's near its head office in South Korea to post a sign reading "No more internal combustion engines", the environmental group said on Monday.
Police said they were investigating the group on suspicion of defacing the advertisement for a sedan next to a busy expressway in the capital, Seoul.
Greenpeace spokesman Sean Lee said the group wanted to send a message to Hyundai Motor that eliminating internal combustion engines was "no longer a matter of choice".
The sign, visible to travellers making their way home to Seoul on Sunday along the busy expressway after a long holiday weekend, was later taken down.
Hyundai, which together with its affiliate Kia Motors, are the world's fifth-largest automaker by sales, reported the incident to the police for investigation, a police official said by telephone.
Hyundai had no immediate comment.
Climate groups like Greenpeace have been stepping up their action around the world against car makers developing big, heavy cars and vehicles with internal combustion engines.
Police said a person responsible for defacing the billboard could face up to three years in prison or a 7 million won (nearly $6,000) fine for property damage, the police official said.
Lee In-sung, a Greenpeace Seoul office campaigner handling legal affairs, said the group was aware of the possible criminal charges but it would carry on with its non-violent action "perhaps in a different form". (Reuters)