Iran's Intelligence Minister has accused the United States of spying on the country's nuclear sites.

Iran's state-run news agency (IRNA) quoted Ali Yunesi as saying the United States has been using satellites and other tools to spy on Iran for a long time.

Earlier this week, the Washington Post reported that unmanned surveillance drones have been flying over Iran for almost a year to search for evidence of nuclear weapons programs and detect weaknesses in air defenses.

Meanwhile, the head of the U.N. nuclear agency says there has been no evidence so far to support U.S. suspicions that Tehran is developing nuclear weapons.

In an interview with four U.S. newspapers (including the Post), Mohamed ElBaradei also called for greater U.S. participation in diplomatic efforts to engage Iran and North Korea in talks about their nuclear programs.