Ukrainian prosecutors said Wednesday they had opened a criminal investigation into the alleged poisoning of a leading candidate in presidential elections scheduled for next month.

The candidate, former prime minister Viktor Yushchenko, became sick more than two weeks ago, and his campaign charged that he was poisoned by political opponents. The allegations have brought new rancor to an already heated race to replace Leonid Kuchma as president.

Yushchenko, a leading opposition figure who is running neck-in-neck with the ruling party candidate, became ill Sept. 6 and was hospitalized in Austria. After he was discharged Saturday, doctors in Vienna said it was possible that he had been poisoned, but they could not confirm it.

Prosecutors said in a statement that they were investigating charges of "attempted murder of a statesman or a public figure." They offered few other details, and did not indicate whether authorities had substantiated the poisoning charges or identified any suspects.

Ukrainian lawmakers voted overwhelmingly Tuesday to set up a commission to investigate the incident.

Neither Kuchma, who decided not to run for reelection, nor Prime Minister Viktor Yanukovych, Yushchenko's main opponent who is the president's designated choice in the Oct. 31 presidential race, have commented publicly on the allegations.

A number of Kuchma's allies however have suggested that Yushchenko had merely eaten spoiled sushi.

In his address to deputies on Tuesday, Yushchenko accused Kuchma's administration of "being capable of brewing political assassinations." He appeared haggard, with his face red, swollen, partially paralyzed and with one eye continually tearing.

Voters in this former Soviet republic of 48 million have become increasingly disenchanted with Kuchma's decade-long rule. His administration has been marred by a series of scandals, rampant corruption and dozens of suspicious deaths of political opponents and opposition journalists.