Stockholm (DPA) -- The fatal stabbing of a Swedish university teacher has raised fears that he was killed over his research that focused on the persecution of minorities in the Ottoman era, a newspaper report said Saturday.

Fuat Deniz, 40, died Thursday after being stabbed Tuesday at Orebro University, west of Stockholm.

Turkish-born Deniz, a Christian Assyrian, moved to Sweden in the 1970s with his parents.

His research and writings included the persecution and killings of the Assyrians during World War I in the Ottoman Empire.

'There is a threat against all who conduct research on Assyrians and the mass murders in the Ottoman Empire,' history professor David Gaunt at Sodertorn University College, south of Stockholm, was quoted saying in the Svenska Dagbladet newspaper.

Gaunt, whose research is in the same field, attended several debates and seminars with Deniz. At times people claiming to be reporters appeared and took photos of those attending the seminars, he recalled.

Gaunt said he also knew of other colleagues who had been harassed and threatened, and he himself had been smeared in a leading Turkish newspaper.

'Even if the threats are not always direct, they have been implied. It is a very sensitive issue where research is seen as a political act,' Gaunt said.

Police have no trace of the assailant.