Greenpeace activists on Thursday draped a banner over Warsaw's highest tower to demand that Russia free fellow members jailed over an Arctic drilling protest.

The three activists hoisted themselves down ropes from the observation deck to hang the huge yellow banner that read "Save the Arctic! Free our activists!" onto the Palace of Culture and Science in the Polish capital's city centre.

Hanging at a height of around 100 metres (330 feet) the banner partially covered a green sign promoting the UN's difficult COP19 climate change talks that began here last week.

Russia had held 30 crew members of Greenpeace's Arctic Sunrise ship since September after they scaled an oil rig in the Barents Sea owned by energy giant Gazprom to protest against oil prospecting.

But, in a gradual climbdown, authorities have now freed on bail 11 activists in a case that has drawn calls for release from high-level politicians and stars such as Madonna and Paul McCartney.

Fifteen more have been granted bail but not yet released while decisions are pending on three others. One activist from Australia has been refused bail.

Warsaw's landmark Palace of Culture and Science, at a height of 231 metres, is a popular location for banners and a frequent image on city postcards.

It is also an object of scorn for many Poles for its ties to the former communist regime: the Soviet Union built the Stalin-era tower in the severe style of socialist-realism just after World War Two.

The "Save the Arctic" banner was the second Greenpeace stunt since the start of the climate talks.

On Monday, the group hoisted banners protesting against coal use atop the economy ministry, prompting police to detain 34 activists.

Greenpeace was also one of six green groups to walk out of the climate negotiations on Thursday, saying the ailing talks were "on track to deliver virtually nothing".

[Image via Agence France-Presse]