Dutch Greenpeace activists Faiza Oulahsen and Mannes Ubels have been released from prison in St. Petersburg after they were granted bail by a Russian court on Wednesday, Dutch media reported on Friday.

Among 30 activists on board Greenpeace's Arctic Sunrise ship, they were detained on Sept. 19 by the Russian authorities after attempting to stage a protest against oil drilling at Prirazlomnaya platform in the Pechora Sea.

"At the moment it remains unclear whether the two have to stay in St. Petersburg or not," Greenpeace spokesperson Sigrid Deters told Xinhua. "We still haven't heard the exact conditions of the bail," she added.

The group was originally arrested and indicted for piracy and could, according to Russian law, be imprisoned up to 15 years.

Some other activists on board of the Arctic Sunrise ship have been released on Monday and Tuesday. The court in St. Petersburg ruled that the activists would be released upon paying a bail of 2 million rubles (62,500 U.S. dollars) each.