The United States rejected on Monday Iran's accusation that Washington was behind the killing of an Iranian scientist and urged Tehran not to use the case to distract attention from its nuclear dispute.
Darioush Rezaie, 35, a university lecturer, was killed by gunmen in eastern Tehran on Saturday. Some media reports said Rezaie was a nuclear scientist but Deputy Interior Minister Safarali Baratlou said this was not true.
Parliament Speaker Ali Larijani, in a speech broadcast live on Iranian state television, blamed the United States and Israel for the killing.
"We were not involved," said State Department spokeswoman Victoria Nuland, expressing U.S. sympathy to Rezaie's family and noting that Tehran frequently blames the West for such events.
"We hope that Tehran is not planning to use this incident to distract attention from what it needs to do, which is to come back into compliance with international obligations."
Several nuclear scientists have been assassinated in Iran in the last few years amid Tehran's intensifying showdown with the international community over its suspected nuclear arms ambitions.
Iran, a major oil producer, says its nuclear program is solely for civilian purposes and so far has refused to halt its sensitive uranium enrichment activities, as demanded by the U.N. Security Council.
The refusal has led to the imposition of sanctions by the United Nations, the European Union and the United States.