Correction: An earlier version of this story had a headline that misstated the number of people charged with piracy.

Greenpeace activists demonstrate at a gas station in Berlin for the release of environmental activists detained in Russia after attempting to board an Arctic oil-drilling rig. (Maurizio Gambarini/European Pressphoto Agency)

Russian authorities turned their informal descriptions of Greenpeace activists as pirates into legal charges Wednesday, the latest escalation in a saga that began two weeks ago as a protest against drilling in the Arctic.

Prosecutors charged 14 people — including a British journalist — with piracy, which carries a maximum penalty of 15 years in prison. An additional 16 await formal charges. All 30 had been ordered detained for two months while the investigation proceeds.

The detentions and accusations of piracy have angered not only Greenpeace and human rights organizations around the world but also environmentalists across Russia, along with one of the country’s most revered rock stars, Yuri Shevchuk.

Two weeks ago, the American captain of the Greenpeace ship Arctic Sunrise, who is among those still awaiting charges, sailed near an oil rig in the Pechora Sea owned by a subsidiary of Gazprom, the energy giant controlled by the Russian government. Activists in inflatable boats approached the platform, and two were detained as they tried to climb onto it and raise a banner.

The next day, members of the Russian coast guard boarded the Arctic Sunrise in international waters, seized the ship at gunpoint and towed it to the northern city of Murmansk, where it arrived Sept. 24.

Even before the ship reached Murmansk, more than 50 Russian environmental groups had signed a letter to President Vladimir Putin asking him to release the activists. The petition, organized by the World Wildlife Fund’s Russian branch, said the drilling project had been extensively criticized by Russian experts concerned with safe oil and gas extraction.

“Detention of environmental activists looks especially cynical in Russia’s Year of Environmental Protection,” the letter said.

Russian prosecutors, who declined further comment until all 30 have been charged, said Greenpeace put workers aboard the oil rig — which is expected to begin pumping by the end of the year — in danger.

Greenpeace said it had launched the protest because the platform threatens the fragile Arctic environment, describing the rig as poorly built and ill-equipped to deal with oil spills.

The arrests were an attempt to intimidate Greenpeace, Human Rights Watch said, alluding to Russian law, which defines piracy as an assault on a ship. The oil rig is on a platform that cannot move.

Kumi Naidoo, Greenpeace International’s executive director, called the charges an assault on the principle of peaceful protest. “Any claim that these activists are pirates is as absurd as it is abominable,” he said in a statement. “It is utterly irrational, it is designed to intimidate and silence us, but we will not be cowed.”

Those charged with piracy Wednesday include Kieron Bryan, a British videographer who was documenting the protest, and Dmitri Litvinov, an activist with Swedish and American citizenship, as well as the ship’s doctor and cook.

The captain, Peter Willcox, is an American who was captain of Greenpeace’s Rainbow Warrior when it was blown up by French security agents in 1985 during a journey to protest French nuclear weapons testing in the Pacific. Naidoo called the arrests the most serious threat to Greenpeace’s peaceful environmental activism since that time.

In an interview on Ekho Moskvy Radio on Wednesday, Shevchuk, the rock singer, dismissed the piracy charges as ridiculous.

“The whole world knows Greenpeace,” he said. “Greenpeace is the organization that helped save the Antarctic . . . and penguins and scientists live there happily. And what about saving whales?”

Then he said he had a secret to reveal: He had planned to sail with the ship himself. He had even bought warm clothes. He had a ticket to Norway, where he would have met the ship. At the last minute, he said, family reasons prevented him from going. “I am really sorry about it,” he said.

“They are hooligans, of course,” he quipped about the activists, apparently likening them to the three young women convicted of hooliganism last year for singing a protest song in Moscow’s main cathedral. The Pussy Riot members were sentenced to what was widely considered an excessive two years in a labor camp.

Now, some activists have begun referring to the Greenpeace ship as the Pussy Sunrise.