Iran's Supreme Court has approved the death sentence of an Iranian researcher accused of spying for Israel.

Ahmad Reza Jalali, who has been jailed since April 2016, was shown on state TV earlier this month confessing to providing information to Israel's Mossad spy agency about Iranian military and nuclear scientists, including two who were assassinated in 2010.

It was not clear if he was speaking under duress. Rights groups say detainees in Iran are often denied due process.

The semi-official ISNA news agency reported the court's decision on Monday. It is not clear when the sentence will be carried out. The ruling is not subject to appeal.