Supporters of former Ukrainian prime minister Yulia Tymoshenko have started a sit-in outside the Kyiv courthouse to protest her arrest.

At least 100 supporters, including some members of the Ukraine parliament, pitched 30 tents Saturday and said they would maintain a vigil until authorities released the 50-year-old former leader. Ms. Tymoshenko was arrested in the courthouse on Friday and hauled off in a prison van to a detention center where she spent the night.

Ms. Tymoshenko was arrested on a contempt of court charge after she repeatedly mocked the judge and witnesses at a trial on allegations that she abused her power as prime minister. Prosecutors allege that she signed a natural gas import contract with Russia in 2009 that was not advantageous to the Ukraine and cost the country $190 million.

She claims the allegations are politically motivated, an attempt by her rival, President Viktor Yanukovych, who defeated her in last year's presidential election, to keep her out of next year's parliamentary elections and the next presidential balloting in 2015.

Several Western countries voiced concern about her arrest, with Germany saying that the investigation of the previous Kyiv government “awakens a suspicion of politically motivated justice.”

U.S. Senator John McCain, who lost the 2008 presidential election to President Barack Obama, condemned her arrest as a violation of basic rights in a democracy.

His statement on Ms. Tymoshenko's website said that “ultimately, what is at stake is the future of freedom and democracy in Ukraine.”

During her trial, Ms. Tymoshenko has refused to stand when addressing the judge and mocked him with comments on the Twitter social networking site. Shortly before her arrest, the current Ukrainian prime minister, Mykola Azarov, testified against her. Ms. Tymoshenko described him as a “fully certified, corrupt old man.”

In a chaotic scene, her supporters in the courtroom attempted to block riot police from arresting her and later unsuccessfully sought to block the prison van from driving her to the detention center.

The judge did not say when her trial will resume.