Scotland Yard said yestersay it is treating the death of a dissident Bulgarian broadcaster, who said he had been attacked by a man wielding a poisoned umbrella, as murder.

The man, Georgi Marcov, 49, died in a hospital Monday. Scotland Yard has called in germ warfare experts to assist in the investigation.

Moscov had told friends that a man he did not know stabbed him in the leg with the point of an umbrella on a London street last Thurday.

Earlier he had said he believed his life was in danger because of his anti-Communist broadcasts to Communist-ruled Bulgaria for Radio Free Europe and the West German Deutsche Welle.

Marcov's wife said that before her husband's defection to the West in 1969 he had been a friend of Bulgarian leader Todor Zhivov. Marcov had become increasingly bitter recently, she said, because of the Bulgarian government's refusal to let him return to visit his dying father last year.

"Georgi was so incensed that his broadcasts for Radio Free Europe became absolutely vitriolic," Mrs. Marcov said.

"He named the mistresses of higher-ups, really smearing mud on the people in the inner circles. His father's death made him more and more angry and determined to cause embarrassment."