Major Safa al-Battat, a former Iraqi army officer who defected to the opposition, is now in a British hospital after taking the thallium in a bottle of locally-made Coca-Cola.
On Saturday an announcer who had worked for the opposition radio based in Kurdistan, beyond Iraqi lines, died from thallium poisoning.
Iraqi intelligence has often employed thallium, a heavy metal that is used in some rat poisons, to assassinate its opponents in the past.
Thallium is usually fatal but acts slowly enough for the poisoner to escape. The Foreign Office said yesterday that British doctors have confirmed that Major al-Battat, who is now in a Cardiff hospital, is suffering from thallium poisoning.
The aim of the government in Baghdad is evidently to show that it can reach its opponents even when they have reached apparent safety in Kurdistan.
The assassination campaign, which was started last November, is also in keeping with harsher measures that have been employed over the last six months by the President of Iraq, Saddam Hussein.
These measures, which include the amputation of the hands and ears of deserters and criminals, are intended to maintain the President's authority over the country.
"I was operating in the south of Iraq in the marshes around Basra," said Major al-Battat in a telephone interview.
"All members of my group used to be officers in the Iraqi army so we were dangerous to them."
He had gone north to Kurdistan where his organisation had its headquarters - Iraqi lines are easy to cross - when he was poisoned.
He thinks that the thallium had been put into a bottle of locally made Coca-Cola somebody gave him but says he cannot prove this.
The first symptoms of thallium poisoning resemble flu and later typhoid fever.
Doctors only correctly diagnosed thallium when they noticed that Major al-Battat's symptoms were the same as those of two Iraqi dissidents who were poisoned in Kurdistan in 1992. The two dissidents had fled there following a failed assassination attempt on President Saddam Hussein.
An official of the Iraqi National Congress said they had intercepted one Iraqi agent with a file of thallium poison. Major al-Battat says he was first brought to Syria but doctors were unable to treat him, apart from giving him pain killers. Permission was then sought from the Foreign Office to bring him to Britain.
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