Russia on Thursday released on bail three Greenpeace activists, including a photojournalist, bringing to four the number freed after two months in prison over an Arctic protest.

Photographer Denis Sinyakov, Greenpeace press secretary Andrei Allakhverdov and the ship's doctor Yekaterina Zaspa all left detention after being granted bail by Saint Petersburg courts, the group said.

Sinyakov's detention over the September protest at a state-owned oil rig was particularly controversial because he is a well-known photographer who was working for Greenpeace as a freelancer.

Sinyakov, who has grown a beard in prison, raised a fist in triumph after stepping out of the notorious Kresty prison. He and Allakhverdov hugged their wives in a video released by Greenpeace.

On Wednesday evening, the first Greenpeace activist, Brazilian Anna Paula Maciel, walked out of her Saint Petersburg prison, smiling and holding a sign saying "Save the Arctic."

Greenpeace campaigner Mikhail Kreindlin told AFP that Maciel had given investigators her address in Saint Petersburg and it was not clear whether she could leave Russia.

After treating the crewmembers harshly on their arrest, the Russian authorities have gradually climbed down, reducing their charge from piracy to hooliganism and now sanctioning their release.

But the activists still face the charge of hooliganism that could lead to a jail sentence of up to seven years.

The jailing of the 30 prompted calls for their release from politicians including British Prime Minister David Cameron as well as stars such as Madonna and Paul McCartney.

On Thursday, a court granted bail to Jon Beauchamp of New Zealand, Greenpeace said. He has yet to be released.

This week, two courts in Saint Petersburg have ruled to release 21 crewmembers on condition that they pay bail of 2 million rubles ($60,750).

But a court extended the detention of one crewmember of Greenpeace's Arctic Sunrise ship, 59-year-old Australian radio operator Colin Russell, until the end of February.

Australia's ambassador to Russia, Paul Myler, wrote on Twitter that he would visit Russell Thursday.

Greenpeace called the decision to keep Russell in jail baffling. Those granted bail include the two activists who actually scaled the oil rig during the September 18 protest in the Barents Sea.