Ukraine said on Friday it will have to negotiate a new gas deal with Russia because of previously-undisclosed plans to break up the republic's existing energy company.

The unexpected announcement came in the heat of the two neighbors' second spat over gas prices in three years and appeared part of a Ukrainian effort to force Russia to ease its negotiating stance over prices.

Activists from Ukraine's scandalous FEMEN group staged a topless protest Tuesday in a show of anger against the entire political class amid the trial against former prime minister Yulia Tymoshenko.

Two young women climbed on the roof of a police truck parked in the courthouse area and quickly stripped from the waist up, an Agence France Presse photographer reported from the scene.

France on Thursday said it had summoned the Ukrainian ambassador in Paris to express its "serious concern" over the arrest of former prime minister Yulia Tymoshenko.

The envoy was told that France would continue to follow very closely the developments in the case that saw Tymoshenko's arrest on Friday for contempt of court in her abuse of power trial, a foreign ministry spokeswoman said.

A methane gas explosion at a mine in eastern Ukraine injured 26 people Thursday less than a week after two accidents in the same area claimed the lives of 37 miners.

The blast occurred the Lugansk region's Krasnokutska mine at 11:40 am local time (08:40 GMT) at a depth of 155 meters while 224 miners were working, of whom 37 were in the impact zone.

The death toll rose to 25 Saturday from two separate coal mining accidents on the same day in Ukraine's eastern industrial district, notorious for its poor safety standards.

The Ukrainian emergency ministry raised the toll from 16 to 18 from an explosion early Friday at the Sukhodolskaya-Vostochnaya coal mine in the eastern Lugansk region.

A blast at one coal mine in eastern Ukraine and an elevator collapse at another killed at least 17 people and injured 11 on Friday, officials said. Nine miners are still missing following the blast.

The twin accidents in eastern mining regions shocked the country and highlighted the persistent dangers of the local mining industry, believed to be one of the world's most dangerous because of outdated equipment and widespread disregard for safety regulations.

A two-headed snake has gone on display at a zoo in southern Ukraine.

The "Skazka" (Fairy tale) zoo in the Crimean city of Yalta on the Black Sea said Wednesday that the albino California Kingsnake has two heads that think, react and eat separately, though one is more passive than the other.

Ukraine's ex-prime minister Yulia Tymoshenko on Friday went on trial for alleged abuse of power, denouncing her rival President Viktor Yanukovych as a coward fearing political competition.

The former premier, known as the "Iron Lady", is accused of abuse of power in connection with a contract she signed with Russian Prime Minister Vladimir Putin after a brief interruption of gas deliveries from Russia in early 2009.

Ukrainian prosecutors on Tuesday denied arresting former Prime Minister Yulia Tymoshenko after the pro-Western leader's party said she had been taken into custody.

The 2005 Orange Revolution leader has been repeatedly summoned for questioning on charges that she defrauded the state out of millions while serving as head of ex-Soviet state's government.

The kidnapping of seven Estonians brought back fears about the resumption of abductions that were common during the 1975-90 Lebanese civil war amid reports that the men could have been snatched to be used as a bargaining chip for a Palestinian recently arrested in Ukraine.

The Estonian tourists cycling in the eastern Bekaa Valley were kidnapped on Wednesday by armed men.