A new US bomb designed to hit Iran's underground nuclear sites has been spotted for the first time - but the images were quickly taken down amid security fears.
The US military posted pictures of a powerful bomb designed to penetrate deep into the earth and destroy underground facilities that could be used to enrich uranium.
Rare images of the weapon, the GBU-57, known as the "Massive Ordnance Penetrator" were posted on May 2 but were suddenly taken down.
According to officials, the photographs revealed sensitive details about the weapon's composition and punch.
The publication of the photographs comes as Iran is making steady progress in constructing a nuclear facility that is likely beyond the range of the GBU-57, which is considered the US military last-ditch weapon to take out underground bunkers.
The US developed the Massive Ordnance Penetrator in the 2000s as concerns grew over Iran hardening its nuclear sites by building them underground.
The Air Force posted images of the bombs on the Facebook page for Whiteman Air Force Base in Missouri.
The base is home to the fleet of B-2 stealth bombers, the only aircraft that can deploy the bomb.
In a caption, the base said it had received two Massive Ordnance Penetrator bombs so a munitions squadron there could "test their performance."
It is not the first time the Air Force has published photos and videos of the bomb that coincided with rising acrimony with Tehran over its nuclear program.
In 2019, the U.S. military released a video of a B-2 bomber dropping two of the bombs. The Air Force did not respond to requests for comment on why it posted - and removed - the most recent set of photos.
The latest photos revealed stencilling on the bombs that listed their weight as 27,125 pounds.
It also described the bomb as carrying a mix of AFX-757 - a standard explosive - and PBXN-114, a relatively new explosive compound, said Rahul Udoshi, a senior weapons analyst at Janes, an open-source intelligence firm.
The weight of the bomb, judging from the stencilling, shows the majority of it comes from its thick steel frame, which allows it to chew through concrete and soil before exploding. However, it remains unclear what the exact effectiveness of the weapon would be.
The Warzone, an Internet news site, first reported on the publication of the photographs.
Within a day, the Facebook post vanished.
Mr Udoshi said the Air Force likely took them down because they revealed too much data about the bombs. "Immediate removal from the internet without comment (or) justification means there is a potential lapse."
