Explosions were heard near the Iranian island of Kharg in the Persian Gulf, where a key oil terminal is located, Reuters and the semi-official Fars news agency reported.
However, the origin of the explosions remains unknown.
The state-affiliated Nournews agency reported, citing unconfirmed reports from local sources, that an Iranian tanker was attacked near Kharg with a missile fired by US forces.
A Fars correspondent on the island indicated that explosions were heard from the Persian Gulf region, but no smoke was seen.
Two days ago, US President Donald Trump said that Washington was ready to launch more strikes on the Middle Eastern country, adding that the duration of the military action did not matter to him.