Iran's navy reports the Strait of Hormuz is closed after firing it warning shot at a vessel
The reports from state media come after Iran's Supreme Leader vowed revenge over the death of his father, Ayatollah Ali Khamenei.
Iran's Revolutionary Guards (IRGC) navy says it has closed the Strait of Hormuz "until further notice" after firing what it described as a warning shot at a vessel it claimed was using an unauthorised route.
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According to Iranian state media, the ship stopped after being struck by the warning shot.
The move follows comments on Saturday from Iran's Supreme Leader Ayatollah Mojtaba Khamenei, who vowed revenge over the death of his father, Ayatollah Ali Khamenei.
In a written message published on Telegram following his father's funeral, Khamenei said avenging the former leader was "the demand of the nation" and "must certainly" take place.
He added: "We pledge to avenge the blood of the martyred leader and all the martyrs of these two wars from the criminal and disgraced killers."
Read more: Trump threatens to 'completely decimate and destroy' Iran if it makes an attempt on his life
The latest escalation comes after the US demanded Iran publicly declare that the Strait of Hormuz remains open to commercial shipping and commit to ending attacks on civilian vessels.
Speaking to reporters on Friday, US officials said the message had been passed to Tehran through regional mediators.
The demand followed attacks on three commercial tankers earlier this week, which triggered an exchange of strikes between Iran and the US.
American media reported Iran later told US officials the attacks had been carried out in error by a rogue faction.
Although President Donald Trump declared the ceasefire "over," he noted that negotiations to end the conflict would still move forward.
Mr Trump has also warned Iran of severe consequences if Tehran targets him.
Writing on Truth Social on Saturday, he said: "1000 Missiles are Locked and Loaded and aimed at the Islamic Republic of Iran, with thousands of more to immediately follow, should the Iranian Government act on its threat, pronounced in many corners of the Globe, to assassinate, or attempt to assassinate, the sitting President of the United States of America, in this case, ME!"