Iran's Revolutionary Guards on Sunday said the US gave a "Hollywood" account of an encounter between the two states' navies in the Gulf, after Washington said Tehran's vessels had harassed its ships.

The US Department of Defense had accused Tehran of dangerous and provocative actions on Wednesday, saying 11 of the Guards' vessels "repeatedly crossed the bows and sterns of the US vessels at extremely close range and high speeds".

The Islamic Revolutionary Guard Corps (IRGC) said in a statement on its official website that the US Navy "has presented an incorrect and agenda-fuelled narrative of this encounter, which shows the Americans' interest in Hollywood stories".

It accused the US of "blocking the path" of Iranian ship Shahid Siavoshi on April 6 and 7 with "dangerous behaviour while ignoring warnings".

The IRGC in response increased maritime patrols, the statement said, and encountered American warships on April 15.

The 11 patrol boats "forced them to draw back from the path of Sepah (IRGC) vessels, despite the provocative and unprofessional actions" of US ships, which ignored warnings.

According to a US Navy statement, Navy and Coast Guard ships were conducting operations in international waters in the northern Gulf with Apache attack helicopters.

"We advise Americans to follow international regulations and maritime protocols in the Persian Gulf and Sea of Oman and avoid any adventurism and false stories," the IRGC said.

It warned that any "miscalculation will receive a decisive response".

Tensions have risen between the two arch foes since the US withdrew from a landmark nuclear deal and reimposed sanctions on Iran in 2018.

They escalated when Washington killed IRGC top commander Major General Qasem Soleimani in a drone strike in January.