Former Ukrainan Prime Minister Yulia Tymoshenko, a galvanizing figure in the Orange Revolution of 2004, has been named a suspect in the murder of a powerful businessman and lawmaker and three others in 1996.
Supporters of Tymoshenko, who is serving a seven-year sentence in a separate case, say the accusations are just the latest in an attempt by President Viktor Yanukovich to keep his rival behind bars.
Tymoshenko's political party said the latest allegations represented a "shameful day in the history of the Ukrainian law enforcement system," The Associated Press reported.
The prosecutor's announcement comes as the European Court of Human Rights is expected to rule that Tymoshenko's current imprisonment is illegal. The fiery opposition leader's party said the the new case is just a way for the government to keep her in jail when that happens.
"Understanding that the European Court of Human Rights will put an end to the dirty and empty tricks against Yulia Tymoshenko in the near future, Yanukovich's associates have resorted to a desperately brazen and mendacious step," the Fatherland party said in a statement.
"They are no longer hiding that they want to hold not only the opposition leader but all of Ukraine behind bars for life," it said.
The European Union has called her jailing "selective justice."
The 52-year-old is suspected of "ordering and organizing" a hit on the life of Yevhen Scherban and three others, who were shot to death as they stepped off an airplane, the Prosecutor General's Office said on its website.
Scherban was a member of Parliament and one of Ukraine's richest men. At the time of the killing, Tymoshenko was a prominent gas trader. Prosecutors said the alleged hit appeared to stem from a business rivalry.
Tymoshenko has not yet been formally charged, but the announcement of her status as a suspect paves the way for prosecutors to pursue charges.
The latest allegations come just weeks before the European Court of Human Rights is expected to issue a ruling on the detention of Tymoshenko.
She is serving a seven-year sentence for abuse of power for ordering a gas deal with Russia in 2009. Prosecutors claimed she did not have cabinet approval to proceed with the deal and that it is was detrimental to Ukraine's economy. She denied the charges.
Tymoshenko said she believes her prosecution and detention are politically motivated and that she has not been granted judicial review, the court said in a news release. She also complained about inadequate jail conditions, according to the release, and said she has not been afforded proper medical care for her health issues, which reportedly include a debilitating back condition.
On Friday, her attorney, Serhiy Vlasenko told the AP that when he tried to visit his client recently, she was unresponsive for several minutes. Doctors said she had taken sedatives and was in satisfactory condition.
Tymoshenko co-led the Orange Revolution in 2004, when hundreds of thousands of Ukrainians protested in response to allegations of widespread fraud in the election of Viktor Yanukovich over rival Viktor Yushchenko.
Thousands of Ukrainians occupied the center of Kyiv, insprired by the fiery speeches of Tymoshenko, and the movement only grew until the election results were voided and Yushchenko was elected president in a new vote.
Tymoshenko briefly served as acting prime minister in 2005. She was elected in December 2007 and served until March 2010.
She was convicted on the abuse of power charges in October 2011 and was banned from holding public office for three years.
The imprisonment of Tymoshenko has contributed to unrest in the country.
The Oct. 28, 2012 election was marred by claims of stuffing the ballot box.
That anger boiled over in December when a brawl erupted in the newly elected Parliament.