Greenpeace has apologised to the people of Peru after the government accused the environmentalists of damaging ancient earth markings in the country’s coastal desert by leaving footprints in the ground during a publicity stunt meant to send a message to the UN climate talks delegates in Lima.

A spokesman for Greenpeace said: “Without reservation Greenpeace apologises to the people of Peru for the offence caused by our recent activity laying a message of hope at the site of the historic Nazca lines. We are deeply sorry for this.

“Rather than relay an urgent message of hope and possibility to the leaders gathering at the Lima UN climate talks, we came across as careless and crass.”

Earlier Peru’s vice-minister for culture Luis Jaime Castillo had accused Greenpeace of “extreme environmentalism” and ignoring what the Peruvian people “consider to be sacred” after the protest at the world renowned Nazca lines, a Unesco world heritage site.

He said the government was seeking to prevent those responsible from leaving the country while it asked prosecutors to file charges of attacking archaeological monuments, a crime punishable by up to six years in prison.

The activists had entered a strictly prohibited area beside the figure of a hummingbird among the lines, the culture ministry said, and they had laid down big yellow cloth letters reading “Time for Change! The Future is Renewable” as the UN climate talks began in Peru’s capital.

“This has been done without any respect for our laws. It was done in the middle of the night. They went ahead and stepped on our hummingbird, and looking at the pictures we can see there’s very severe damage,” Castillo said. “Nobody can go on these lines without permission – not even the president of Peru!”

Peruvian authorities are also seeking the identity of the archaeologist who led the activists to the site and the plane from which the photos of the stunt were taken, he said. “It was thoughtless, insensitive, illegal, irresponsible and absolutely pre-meditated. Greenpeace has said it was planning this action for months.”

Tina Loeffelbein, a Greenpeace spokeswoman at the summit, said she was not aware of any legal proceedings being brought against the group. She said Greenpeace was cooperating with the Peruvian authorities and seeking to clarify what took place.

In a statement Greenpeace said it was concerned that it could have caused “moral offence to the Peruvian people”.

The statement read: “Our history of more than 40 years of peaceful activism clearly shows that we have always been most respectful with people around the world and their diverse cultural legacies.”

Castillo responded: “Disrespecting humanity’s cultural heritage – I don’t think that’s the message this summit or Greenpeace is trying to spread to the world! Most of us in the cultural sector agree with the message. But the means don’t justify the ends.”

“We took every care we could to try and avoid any damage. We have 40 years of experience of doing peaceful protests,” Kyle Ash, Greenpeace spokesman, told the Guardian. “The surprise to us was that this resulted in some kind of moral offense. We definitely regret that and we want to figure out a way to resolve it. We are very remorseful for any offense that we’ve caused and we’re very remorseful for that.”

He said Greenpeace met on Wednesday with Peru’s minister of culture, Diana Alvarez. He said the organization hoped to maintain a dialogue with the Peruvian government. He added Greenpeace would take “total responsibility” if any permanent damage had been caused to the archaeological site.

“It’s not a matter of money. The destruction is irreparable,” Ana Maria Cogorno, President of the Maria Reiche Association named after the German archaeologist whose groundbreaking research on the Nazca Lines from 1940 onwards saw them gain recognition and protection, told the Guardian.

The hummingbird etching on which the Greenpeace stunt was laid was the “only one of the lines which was completely untouched and perfectly conserved”, she said. “It’s one of the symbols of Peru,” she added.

Last week Greenpeace projected a message promoting solar energy on to Huayna Picchu, the mountain that overlooks the Inca citadel of Machu Picchu, another protected archaeological site in Peru.