The US used six GBU-57 bunker-buster bombs in strikes on Iran’s key nuclear facility in Fordow, which is located deep underground, Fox News reports, citing its sources.

The B-2 bombers are the only aircraft capable of carrying such heavy bombs, each weighing more than 13 tons. The bombers can carry two GBU-57 bombs each.

In the attacks on two other nuclear infrastructure sites in Isfahan and Natanz, around 30 Tomahawk cruise missiles were launched from Ohio-class submarines, according to Fox News.

Isfahan was the most challenging target, notes Fox News correspondent Jennifer Griffin, citing her sources in military circles.