Three oil tankers have exploded and caught fire in the Strait of Hormuz, Iran's Revolutionary Guard Navy said on Sunday, in the latest incident in the vital waterway. The force said the fires began in the early hours of the day, with thick smoke spreading across the strait.

According to Press TV, the Guard said the tankers were travelling along a route Tehran considers unauthorised and had switched off their navigation and identification systems. Al Jazeera's live coverage likewise reported that the Guard described three "rogue oil tankers" as hit by blasts and engulfed in severe fires.

The Guard blamed the fires on what it called the "mischief" of the American military, and warned that vessels defying Iranian rules in the strait would face similar consequences. It did not name the tankers, say which countries they belonged to, or report any casualties, and the claims have not been independently verified.

The announcement came less than a day after the Guard said two other tankers had struck naval mines and caught fire late on Saturday, one east of the strait and one inside the waterway itself. Those vessels were also said to have switched off their positioning systems while using an unauthorised southern route.

Iran has kept tight control over passage through the strait since the war with the United States and Israel began in late February, requiring ships to use designated northern corridors. Roughly one-fifth of the world's oil normally passes through the narrow channel, which links the Gulf with the Gulf of Oman, so every new incident adds to pressure on shipping and energy markets.