The Israeli secret service Mossad was responsible for the assassination last month of an Iranian scientist in Tehran, Germany's Spiegel Online news website reported.

The killing of Dariush Rezaei-Nejad was "the first serious action taken by the new Mossad chief Tamir Pardo," according to an unidentified Israeli intelligence source quoted by Spiegel Online.

Iranian press reports said Rezaei-Nejad was shot five times by unknown assailants as he and his wife were waiting for their child in front of a kindergarten in Tehran on July 23. His wife was wounded in the attack.

The Iranian government blamed the United States and Israel for the attack, the latest in a series targeting Iranian nuclear scientists who are suspected by the West to be working on a nuclear weapon programme.

Tehran denies it has such a programme and insists that its atomic activities are entirely peaceful.

Rezaei-Nejad is believed to have worked on the trigger mechanism for nuclear weapons, Spiegel Online said in its report first published on Monday.