Updated

The investigation into the unsolved 2004 dioxin poisoning of President Viktor Yushchenko has been completely politicized, Ukraine's prime minister said Thursday before she was questioned by prosecutors.

Yulia Tymoshenko suggested that she has being targeted because she is a potential competitor to Yushchenko in the 2010 presidential elections.

"When a person who is considered by the president as his rival at elections is simultaneously accused of state treason and of spying for the Kremlin, and then Viktor Yushchenko summons me to the prosecutors in relation to his poisoning, I think that ... no comment is needed," she told reporters outside the prosecutor's office in Kiev. "Everything is apparent enough."

Yushchenko accused Tymoshenko of teaming up with the Russia-friendly opposition Party of Regions in order to sideline him and "ruin the democratic developments" of Ukraine.

Ukrainian politics have long been marked by bitter feuding between rivals and even allies.

Last week, Yushchenko called for a new governing coalition and threatened new elections, accusing Tymoshenko and opposition parties of attempting a "constitutional coup" by passing legislation that trimmed presidential powers.

Tymoshenko in turn charged that he was seeking to undermine her before a presidential vote and vowed that her government would continue working unhindered.

The two were partners in the 2004 Orange Revolution that catapulted Yushchenko to the presidency. But their tug-of-war has now ruined their coalition and put the county on the brink of its third parliamentary election in as many years.

The poisoning incident came at the height of the 2004 election campaign and left Yushchenko's face badly disfigured. He has suggested the poisoning may have been orchestrated by Russia.