(CNN) The US claims to have multiple images of Iranian commercial vessels in the Persian Gulf that it believes are carrying missiles and other munitions, according to a US official with knowledge of the situation.

CNN has not reviewed the intelligence that has led to the US assessment. The US government has provided no proof the ships are carrying hidden missiles and other munitions.

The freighters have been modified, the official said, with large areas of their decks removed. The officials did not explain why these vessels would need to be altered to carry missiles.

Recent surveillance has shown some of those freighters moving in and out of Iranian ports in recent days, the official added.

At the same time, two US officials said that Iranian naval forces have significantly increased their presence around the Strait of Hormuz in the last two weeks.

Read More