A judge in Ukraine rejected Monday a request by former prime minister Yulia Tymoshenko's lawyer to free her from police detention during her trial on abuse of authority while in office.

Ms. Tymoshenko was taken into custody Friday after the judges determined she was in contempt of court.

On Sunday, the administrative court decided to ban mass protests near the Kyiv court where the trial will take place. Security troops also surrounded her supporters near the detention center in Ukraine's capital where she is being held.

The U.S. embassy in Kyiv has called on Ukraine to release the former prime minister. A statement issued Saturday also expressed concerns about the application of the rule of law in the Eastern European country.

Ms. Tymoshenko is accused of overstepping her powers in the process of striking a natural gas deal with Russia in 2009.

Prosecutors say the deal was not advantageous to Ukraine and cost the country $190 million. She denies the charges.

Russia's Foreign Ministry said Friday that the 2009 gas agreement was signed in conformity with Russian and Ukrainian law on orders from the Russian and the Ukrainian presidents.

The EU's foreign policy chief, Catherine Ashton, and Enlargement Commissioner Stefan Fuele issued a statement late Friday calling for an independent and transparent trial.

An official in Britain's Foreign Office said Saturday his country will closely monitor Ms. Tymoshenko's trial and the cases against some of her former officials.

Ms. Tymoshenko says the trial is a part of a political vendetta by President Viktor Yanukovych.

She was a central figure in Ukraine's 2004 pro-Western Orange revolution, which helped bring to power Mr. Yanukovych's rival, former president Viktor Yushchenko. Mr. Yanukovych became president last year after defeating Ms. Tymoshenko.