PARIS (AP) _ A French hostage said to have been executed by his Lebanese captors has been buried in a cemetery in southern Beirut, the hostage's wife said.

In a book to be published at the end of the month, Mary Seurat says the death of her husband, Michel, a noted Middle East researcher, was confirmed to her in January by a ''technical counselor'' involved in hostage negotiations.

The counselor, whose name and nationality are not mentioned, told her that Seurat died at the end of 1985 and was buried in Raoudat-Al-Chahidayn cemetery.

Seurat was kidnapped in Lebanon May on 22, 1985, along with French journalist Jean-Paul Kauffmann, two months after the kidnappings of diplomats Marcel Carton and Marcel Fontaine.

On March 5, 1986, the Islamic Jihad, a pro-Iranian Moslem Shiite group, announced Seurat had been executed. His body has never been found.

''Those who serve the state, just like the terrorists, would have maintained the incertitutude (of Seurat's death) until the end,'' Mrs. Seurat writes in her book, ''The Ravens of Aleppo.''

The government has not officially said it believes Seurat to be dead, but his name is not normally evoked in references to French hostages.

Mrs. Seurat has long been convinced of her husband's death, despite the official silence. Long ago, she asked a French TV station that shows photographs of the captured Frenchmen before each nightly newscast to remove the picture of her husband.

Kauffmann, Carton and Fontaine are still being held in Lebanon, along with 18 other foreigners, including nine Americans.

The hostage held longest is Terry Anderson, chief Middle East correspondent for The Associated Press. He was kidnapped three years ago Wednesday.