news of the first incident was revealed by the pentagon after iranian guards seized mv maersk tigris this week , by firing warning shots across the vessel 's bows .
ranian patrol vessels fired warning shots across the bridge of the marshall islands-flagged cargo vessel the maersk tigris tuesday morning and seized it for trespassing just days after it had ` harassed ' another ship .
in the april 24 incident , four iranian patrol boats with the country 's elite revolutionary guards ` harassed ' a us-flagged commercial ship .