So who poisoned Yushchenko's soup?

It is a story worthy of Frederick Forsyth. The candidate most likely to take the helm of a former Soviet republic, but who has powerful enemies in neighbouring Russia, is disfigured by a deadly poison administered via his soup.

It is a story worthy of Frederick Forsyth. The candidate most likely to take the helm of a former Soviet republic, but who has powerful enemies in neighbouring Russia, is disfigured by a deadly poison administered via his soup.

The mystery is who poisoned Viktor Yushchenko and why? Mr Yushchenko, who believes he was cheated out of the presidency of Ukraine by a fraudulent election, is clear on the second point. "The aim, naturally, was to kill me," he said yesterday outside the Vienna clinic where doctors confirmed he had been poisoned by a dioxin.

If it was an assassination attempt, it was botched. Dioxins can kill. They are a group of chemicals produced as byproducts from factories that use chlorine and which can cause liver damage and cancer. The most dangerous, TCCD, is found in Agent Orange, which was used to devastating effect by America during the Vietnam war.

Mr Yushchenko's doctor, Michael Zimpfer, said: "If this dose had been higher, it may have caused death. Instead, the politician got away with chloracne, a virulent form of acne and a hallmark of dioxin poison. It destroyed his looks but should clear up in about three years.

As a pro-Western politician expected to win last month's election, Mr Yushchenko was not short of enemies and he blames the Ukraine authorities for his poisoning. His opponent Viktor Yanukovych, the Prime Minister, strenuously denies this.

Dioxins spread quickly through the body and the poison was probably administered on the day Mr Yushchenko was taken ill by being mixed with soup or cream. Mr Yushchenko first complained of pains on 5 September after meeting the head of Ukraine's secret service, Ihor Smeshko. But the parliamentary commission which investigated the mystery illness in October lists other places he ate or drank that day. Mr Smeshko promised the secret service would take action.

Supporters of Mr Yushchenko carried their cause to the pro-government eastern heartlands yesterday as campaigning in the country's repeat presidential election race got under way. It follows the "orange revolution" of more than two weeks of street protests against last month's falsified voting results.

The Russian-speaking south-east will be the battleground in the vote scheduled for 26 December. The outcome will determine whether Ukraine will emerge as a unified country or one with deep divisions between the south-east and the central and western regions, which now appear solidly to support Mr Yushchenko.

The Prime Minister is spending most of his time in Donetsk, where he was once governor and can still count on core support.

Important members of Mr Yanukovich's campaign team, including his campaign manager and the former head of the central bank, Serhii Tyhypko, have abandoned him. Yet he is still endorsed by key figures in Russia.

Hundreds of thousands of Yushchenko supporters have already signed up to be volunteers in the campaign.