The US military struck Iran's Qeshm Island on Monday, media outlets reported, citing American officials.
The strike, first reported by The Wall Street Journal, follows Iranian state media reports of several explosions on the island, which is situated on the Strait of Hormuz.
The attack was the latest in a series of limited strikes carried out by Washington in recent weeks, the Journal said.
It added that strikes have been carried out on a smaller scale and purposefully kept secret so as not to signal any intent of resuming its major military campaign against Iran.
Other media outlets described the attack as a defensive measure in response to Iran carrying out strikes on US assets.
US Central Command did not immediately respond to a request for comment.
Oil prices rose in early Asian trade after the report of the strikes, raising concerns about an escalation of the conflict and prolonged disruptions to Middle East oil supplies.
Brent crude futures rose or 0.5 per cent to $105.25 a barrel while West Texas Intermediate crude was also up 0.5 per cent to $96.93 a barrel.
Earlier on Monday, President Donald Trump raised doubts about whether he would follow through on a threatened resumption of military strikes against Iran and said a deal with Tehran could happen.
Asked by reporters if he was considering striking Iran after Tuesday's midterm elections, Mr Trump replied "no".
“We had a war with Iran. We won,” Mr Trump told reporters Monday. “I don’t know if you even call it a war because we haven’t been doing any fighting for months.”
Washington and Tehran have been at war since February 28.
