The LNG carrier Mubaraz, operated by the Emirati national oil company Adnoc, left the Gulf sometime in April with 132,890 cubic metres of LNG on board, having loaded at Das Island in the United Arab Emirates on March 2, according to Kpler data analysed by AFP.

Iranian forces virtually closed off the strait after the United States and Israel launched strikes on the Islamic republic on February 28, prompting Tehran to retaliate across the region.

After peace talks with Iran failed, the US on April 13 launched a counter-blockade, turning back ships coming from Iranian ports and boarding others in Asia, including two oil tankers.

The Mubaraz switched off its AIS transponder at the end of March for a month, before transmitting again off the coast of India on Monday.

"It could be the case that the vessel managed to cross the strait during the weekend of 18-19 April, when multiple vessels attempted to cross the strait (including seven LNG tankers), however this is not yet confirmed," Kpler analyst Charles Costerousse said in a note.

The Sohar LNG was the only LNG carrier to have previously crossed the strait since March 1, but it was empty or very lightly loaded.

The LNG market, in which Qatar is one of the main players, is among the hardest hit by the traffic restrictions in the Strait of Hormuz.

Ship tracking platform MarineTraffic meanwhile reported that a 333-metre (1,000-foot) supertanker, the Idemitsu Maru, crossed on Tuesday laden with oil, passing close to an Iranian checkpoint in the north of the strait. Shipping media identified it as a Japan-linked vessel.

Around 20 percent of global LNG trade normally transits the strait in peacetime.

Trackers and media have in recent days reported several Iranian oil tankers stationary near the strait in a possible hint that the US blockade was preventing them from shipping oil out.

Ship trackers identified the Nasha, an old Iranian oil supertanker recently brought back into service, stationary in the Gulf.

News agency Bloomberg said the Nasha was loaded with two million barrels of oil.

They also reported a cluster of other tankers off the Iranian port of Chabahar, west of the strait towards the US blockade line.

Specialist site TankerTrackers said 20 Iranian tankers without cargo were available for loading but Bloomberg said the total number was not clear.

Regular tracking platforms indicated that the ships' transponders were switched off.