At least two ships sailing from Iranian ports crossed the Hormuz Strait on Monday despite a US military blockade, maritime tracking data indicated Tuesday.
They were among at least four Iran-linked vessels that used the route after Washington's blockade came into effect at 1400 GMT on Monday, according to maritime data provider Kpler.
The Liberia-flagged bulk carrier Christianna crossed after unloading 74,000 tonnes of corn at the Iranian port of Bandar Imam Khomeini, passing Iran's Larak Island in the strait around 1600 GMT on Monday, Kpler data showed.
A second ship, the Comoros-flagged tanker Elpis, was near Larak Island around 1100 GMT and cleared the strait about 1600 GMT.
It was loaded with 31,000 tonnes of methanol, having left the Iranian port of Bushehr on March 31, Kpler data showed.
US Central Command had said the blockade would target "vessels of all nations entering or departing Iranian ports and coastal areas."
A Chinese tanker, the Rich Starry, also crossed the strait overnight from Monday to Tuesday via the Iranian-approved vetting route south of Larak Island.
Kpler said that vessel was carrying 31,500 tonnes of methanol and was bound for Sohar in Oman, according to data from its transponder.
Media including leading shipping journal Lloyd's List interpreted the Chinese ship's passage as a "test" of US President Donald Trump's blockade.
Maritime analysts have cautioned during the recent weeks of conflict around the strait that ships' signals in the region have been disrupted and manipulated, making precise tracking difficult.
Sanctioned ships
The Rich Starry is listed by the United States' Office of Foreign Assets Control as being sanctioned for its ties to Iran.
The Elpis is also under US sanctions for ties to Iran, but the Christianna is not.
Iranian forces effectively closed the strait after the war broke out with US and Israeli strikes on Iran on February 28.
The US on Sunday announced its own blockade after peace talks with Iran failed.
Chinese foreign ministry spokesman Guo Jiakun on Tuesday called the US move "dangerous and irresponsible."
A fourth vessel, the Madagascar-flagged tanker Murlikishan, meanwhile crossed the strait westward into the Gulf on Tuesday morning through the Larak Island route.
It was empty and heading to the Iraqi port of Khor al Zubair, according to its transponder signal, Kpler said.
It is sanctioned by the US for Iran-related trade and many of its past trips to the Gulf had been to Iran, picking up Iranian bitumen and asphalt to ship to Asia.