Iran has arrested several people in the killing of a nuclear scientist last week that Tehran blames on Israel and the United States, parliamentary speaker Ali Larijani told state Al-Alam TV, Tehran Times daily said on Monday.

"We have discovered some clues and some arrests have been made," Larijani told the Arabic-language broadcaster.

Mostafa Ahmadi Roshan, a deputy director of Iran’s largest uranium enrichment plant, died in a car bomb explosion in Tehran last week. Local police sources said a passing motorcyclist attached a magnetic mine to the car Roshan was riding in.