Ukrainian opposition leader Viktor Yushchenko called for a serious investigation to determine how he was poisoned by dioxin, but urged it be conducted after the Dec. 26 presidential runoff election to avoid influencing the results.
Doctors at Vienna's Rudolfiner clinic said tests run over the weekend proved beyond a doubt that it was dioxin poisoning that caused a mystery illness in September that left Yushchenko disfigured and in pain.
"I don't want this factor to influence the election in some way -- either as a plus or a minus," Yushchenko said as he left the Austrian clinic on Sunday and headed back to Kiev.
"This question will require a great deal of time and serious investigation. Let us do it after the election -- today is not the moment," he said.
Following the revelation of the dioxin poisoning, Ukraine's prosecutor general's office said it had reopened the criminal investigation that it closed last month for lack of evidence at the time.
While high concentrations of dioxin remain in his blood, doctors said Yushchenko's organs have not been damaged and he is fit for the campaign trail.
"He has almost made a complete recovery. His liver is fine, his pancreas is fine, but he still has residual pain," hospital director Dr Michael Zimpfer said.
Lawmakers from Yushchenko's party said the clinic's findings confirmed that his opponents wanted to assassinate or disable him rather than take the risk he would defeat Prime Minister Viktor Yanukovych in the presidential election.
Kremlin-backed Yanukovych won the initial presidential runoff, but the Supreme Court voided the vote on fraud allegations.
Yanukovych campaigners rejected suggestions that the prime minister could have been involved in the poisoning.
There is "no logic in such an accusation," said Taras Chornovyl, Yanukovych's campaign manager.
Yushchenko fell ill on Sept. 5 and has been treated at the Vienna clinic twice before.
A lab in Amsterdam, using a newly developed test, found his blood contained more than 1,000 times the normal amount of dioxin, Zimpfer said.
Tests showed the toxin was taken orally, and was likely slipped into something that Yushchenko ate or drank, Zimpfer said, suggesting that whoever was responsible may have thought it untraceable.
Dioxin is a byproduct of industrial processes such as waste incineration and chemical and pesticide manufacturing.
The massive quantities of it found in Yushchenko's system caused chloracne, a type of adult acne caused by exposure to toxic chemicals. The condition is treatable, but can take two to three years to heal.
Also Sunday, Yanukovych's spokesman, Oleh Ternovsky, said that the prime minister wants Ukraine's parliament to form a commission to investigate whether the US helped finance Yushchenko's campaign.