Iran’s top military commander warns that Britain’s illegal seizure of an Iranian oil tanker in the Strait of Gibraltar will not go “unanswered.”

“The capture of the Iranian oil tanker will not go unanswered and Tehran will give a response to [the UK’s] contemptible move at an appropriate time and place when necessary,” Chairman of the Chiefs of Staff of the Iranian Armed Forces Major General Mohammad Baqeri said on Tuesday, according to EIN News.

Gibraltar police and customs agencies, aided by a detachment of British Royal Marines, boarded and impounded Iranian supertanker Grace 1 in the Strait of Gibraltar last week, upon a request from the United States.

Iran’s Foreign Ministry summoned Britain’s ambassador to the country to express its strong protest at the move.