Doctors treating Ukrainian opposition leader Viktor Yushchenko have confirmed he was poisoned with TCDD, the most harmful type of dioxin.

TCDD was a key contaminant in Agent Orange, the substance that caused numerous health problems during the Vietnam War.

The doctors in Vienna say the level was about 6,000 times higher than normal.

In an interview Thursday with the Associated Press, Mr. Yushchenko said he was poisoned at a September dinner with top Ukrainian security officials.

This came as Mr. Yushchenko and Prime Minister Viktor Yanukovych were in the midst of a heated presidential election campaign. The two face off in a December 26 election.

The Associated Press also interviewed Mr. Yanukovych, who said he does not want to be associated with authorities Mr. Yushchenko say poisoned him.

Mr. Yanukovych was declared winner of a flawed November election, but the Supreme Court overturned the results and ordered this month's re-run.

Some information for this report provided by AP.