The U.S. military said it intercepted Iranian attacks Thursday on three Navy ships in the Strait of Hormuz and “targeted Iranian military facilities responsible for attacking U.S. forces," highlighting the fragility of the month-old ceasefire between the two countries.

U.S. Central Command said in a social media post that U.S. forces intercepted “unprovoked Iranian attacks” and responded with self-defense strikes.

The U.S. military said no ships were hit. It said it doesn’t seek escalation but “remains positioned and ready to protect American forces.”

President Donald Trump told reporters in Washington that the ceasefire was holding despite the violence.

“They trifled with us today. We blew them away,” Trump said.

Meanwhile, Iranian state media said the country’s armed forces exchanged fire with “the enemy” on Qeshm Island in the strait. It is the largest Iranian island in the Persian Gulf, home to about 150,000 people. It also houses a water desalination plant.

Iranian state media also reported loud noises and defensive fire in western Tehran. In southern Iran, explosions were heard near Bandar Abbas, semiofficial Iranian news agencies Fars and Tasnim said. The reports did not identify the source of the blasts.

Earlier in the day, a shipping data company reported that Iran has created a government agency to vet and tax vessels seeking passage through the crucial Strait of Hormuz.

The Iranian effort to formalize control over the channel raised new concerns about international shipping, with hundreds of commercial vessels bottled up in the Persian Gulf and unable to reach the open sea. Still, hope that the two-month conflict could soon be over buoyed international markets.