Dhaka, June 23 -- Iran likely filled in tunnels at some of its nuclear facilities ahead of the recent U.S. strikes, according to a Washington-based nuclear nonproliferation group.

The Institute for Science and International Security said satellite images taken by Airbus on Friday showed trucks dumping soil into tunnels at Iran's nuclear site in Isfahan, just days before the American attack early Sunday.

The group believes the U.S. strikes likely targeted the tunnel entrances, reports AP.

"At least three of the four tunnel entrances are collapsed," it said. "The status of the fourth one is unclear."

Iran is also believed to have filled in tunnels at its underground Fordo enrichment facility prior to the American strikes, which may have...