The Pentagon released new images late Monday night which officials said offered more evidence operatives from Iran’s Revolutionary Guard Corps (IRGC) were responsible for last week’s attacks on oil tankers in the Gulf of Oman.

The U.S. military said the photos, taken from a Navy helicopter, showed Iranian forces removing an unexploded mine from the hull of the Japanese-owned Kokuka Courageous oil tanker.

Other photos showed a large hole on the side of the Courageous, above the waterline, that officials said appeared to have been caused by another mine.

The release of the photos came as the U.S. Government works this week to convince members of Congress and allies that the accusations against Tehran are true. Iran has accused America of promoting an “Iranophobic” campaign.

Tehran, however, has repeatedly threatened to close the vital Strait of Hormuz, through which 20 per cent of the world’s oil flows.

“Iran is responsible for the attack, based on video evidence and the resources and proficiency needed to quickly remove the unexploded limpet mine,” the U.S. military’s Central Command said in a statement by way of background to the image selection.

The U.S. military has also accused the IRGC of trying but failing to shoot down a U.S. drone, to disrupt surveillance of the tankers during the attacks.

The Pentagon announced Monday that Acting Defense Secretary Patrick Shanahan has authorized sending another 1,000 troops to the Middle East, following the attacks.

On Tuesday, the Secretary of State, Mike Pompeo, is due to visit the Florida headquarters of U.S. Central Command (in charge of all operations in the Middle East) and U.S. special forces.