Iranian gunboats attacked at least one container ship in the Strait of Hormuz on Wednesday, maritime agencies said, despite US President Donald Trump announcing he was extending a ceasefire to allow more time for peace talks.

The British maritime security monitor UKMTO said one container ship reported it was fired upon by an Iranian Revolutionary Guards (IRGC) boat 15 nautical miles northeast of Oman near the entrance to the strait, causing damage to the bridge but no casualties.

The Iranian news agency Tasnim said the ship had "ignored warnings from Iran's armed forces", which are blockading the strategic waterway, but British security firm Vanguard Tech sad the vessel was sailing under a Liberian flag and "had been informed it had permission to transit the Strait of Hormuz".

Separately, another container ship eight nautical miles west of the Iranian coast was fired upon and stopped in the water, UKMTO said, without identifying the attackers.

Vanguard identified it as the Panama-flagged containership Euphoria, which it said was "transiting outbound of the Strait of Hormuz".

The US Navy is attempting to block vessels heading to and from Iranian ports, while Tehran has said vessels must seek permission to leave of enter the Gulf through Hormuz, through a route that in peacetime accounts for a fifth of the world's oil and gas exports along with other vital commodities.

The US Defence Department said on Tuesday that US forces had intercepted and boarded a "stateless sanctioned" vessel.

Both sides accuse the other of ceasefire breaches.

Before the latest attacks, Trump had said he had pushed back the end of the two-week truce following a request by Pakistani mediators and to give Iran's "fractured" leadership time to form a proposal.

The ceasefire has brought some respite to a region engulfed for weeks in war but, with no agreement yet in place, uncertainty remains and brought little relief to global markets.

Trump said the US blockade of Iran's ports would continue, while Pakistani mediators try to revive a dialogue between Washington and Tehran.

Iran has all but shut the strait in the seven weeks since the United States and Israel launched a massive attack on the Islamic republic that plunged the Middle East into war. (AFP)


Edited by Tony Sabine