KIEV, Ukraine - Ukraine's Supreme Court resumed its probe today into bitterly disputed results from the presidential runoff election, while parliament convened to debate the threat to this ex-Soviet republic's unity.

The simultaneous sessions of Ukraine's highest judicial and legislative branches came amid rising support for an opposition-demanded revote as the best way to avoid splitting Ukraine into a pro-Russian east and pro-Europe west.

Ukraine's government has been paralyzed since the Nov. 21 presidential runoff sent hundreds of thousands into the streets of the capital for round-the-clock protests to support opposition candidate Viktor Yushchenko, who claims massive fraud robbed him of victory.

Ukraine's eastern Russian-speaking regions, which support the declared winner, Prime Minister Viktor Yanukovych, retaliated with threats of autonomy, sparking fears that this eastern European nation of 48 million might break apart.

Outgoing President Leonid Kuchma said Monday he would support a repeat vote.

Yanukovych said Tuesday that if he becomes president, he will offer Yushchenko the post of "first person," or the prime minister's job, according to remarks broadcast on Ukrainian television. Yushchenko's aides have said he would reject such an offer.

In parliament, speaker Volodymyr Lytvyn criticized "many state, regional and local officials in the east and south of the country for inciting separatism ... and unconstitutional and illegal aspirations for independence and autonomy."

The Ukrainian Security Council said today that it had opened a criminal investigation into threats to the country's territorial integrity from officials and other people who "publicly declare the necessity of splitting the southeast regions from Ukraine," the Interfax news agency reported, citing spokeswoman Marina Ostapenko.

The Prosecutor General's Office also launched an investigation.

Parliament tried unsuccessfully to pass a vote of no-confidence in the government due to the appearance of separatist threats in the nation. Only 196 of the 410 lawmakers present supported the measure, less than the 226 votes needed.