KIEV (Reuters) - The Ukrainian women's group, Femen, took its distinctive brand of protest to the trial of ex-prime minister Yulia Tymoshenko on Tuesday when two activists climbed atop a police wagon outside the court and bared their breasts.

The action by the group, whose activists regularly stage topless public protests to dramatize their causes, surprised scores of police who were keeping an eye on a nearby rally by pro-Tymoshenko supporters.

The pair clambered on to the roof of the prison van parked near the Kiev city center courtroom, removed their blouses and jeered at police and the country's politicians who, they said, belonged inside the vehicle themselves.

"This vehicle is reserved for bandits ... the check-out is open," they called from on top of the vehicle before police finally climbed up and managed to carry them down.

The protest brought some light relief to the trial of Tymoshenko who is charged with abuse of office over a gas deal signed with Russia in 2009 when she was prime minister. The leadership of President Viktor Yanukovich says the deal saddled Ukraine with too high a price for its gas imports.

Femen regularly stages protests over women's rights and covers a range of causes from campaigning against sex tourism in Ukraine to the treatment of women in parts of the Middle East.

It takes up an anti-establishment position inside Ukraine and has been as critical of Tymoshenko's record as a politician in the past as it has of Yanukovich whose off-color remarks about women have provided it with pretexts for protests.

Explaining Tuesday's action by Inna Shevchenko, 21, and Oksana Sachko, 23, Femen said it was against "the dirty in-fighting between two criminal gangs being presented to the people as a struggle between good and evil."

Femen activist Alexandra Shevchenko, who did not take part in the protest, said it was intended to remind Yanukovich's Party of the Regions that "when they put the opposition in jail the prison vans are also booked for them."

A spokesman for Kiev city police said the two young women had been detained for "hooliganism." They would either be given a warning or fined, he said.

(Writing by Richard Balmforth)