Iran has managed to export some liquefied petroleum gas and jet fuel since July, despite a US naval blockade, shipping intelligence showed and people involved in security said.

Tehran has in recent weeks been concealing such cargoes among a growing volume of ship-to-ship transfers by other Gulf producers off Oman, four people in maritime security who track Gulf oil movements told Reuters.

The Iranian exports and methodology are reported for the first time here. While a fraction of its former energy exports, the cargoes are rare evidence of petroleum products getting through a blockade that has halted Iran's crude exports.

Analysis by US advocacy group United Against Nuclear Iran (UANI), which monitors Iran-related tanker traffic using ship and satellite tracking, shows at least eight gas tankers carrying Iranian LPG have left the Gulf of Oman since mid-July.

Another tanker carrying Iranian jet fuel reached Myanmar in September, additional satellite imagery and analysis by maritime intelligence group SynMax show.

The US imposed targeted sanctions in 2023 on Myanmar's jet-fuel industry, citing military airstrikes on civilians that the United Nations says have killed thousands of people. Myanmar's military government has repeatedly denied targeting civilians, saying its operations are directed against armed groups.

Six of the eight gas tankers and the jet fuel tanker are under US sanctions for transporting Iranian petroleum and petrochemical products, a Reuters analysis of the vessels and sanctions imposed on ships by the US Treasury showed.

"What we have seen passing is a handful of tankers carrying Iranian LPG, but the overwhelming majority of tankers laden with Iranian products have been redirected by US forces," said Jemima Shelley, senior research analyst with UANI.

Shelley said some Iranian LPG tankers transferred cargoes near the Omani coastal towns of Shinas and Sohar, while others waited in the Gulf of Oman before heading past the US blockade, which US Central Command has said sits across the Gulf of Oman near the Iran-Pakistan border. The total amount of these LPG cargoes was estimated at 4.1 million barrels, Shelley said.

Shelley said the shipments were driven "more by opportunism" than showing a new trend of Iran trying to export its oil and petrochemicals by using smaller ships.

Most of the cargoes sailed to Malaysia's Eastern Outer Port Limits to conduct further STS transfers for likely destinations in China, Shelley said, based on UANI's analysis.

The Iranian government did not respond to a request for comment. Myanmar's military-backed government did not respond to a request for comment on whether the country had received Iranian jet fuel.

The US military's Centcom said its naval blockade, which was first imposed on Iran-related oil exports on April 13, is "ironclad". The blockade was lifted in June after the US reached a draft understanding with Iran, but it was reimposed on July 14 following the collapse of the agreement.

A US military official told Reuters that the passage of a vessel does not necessarily mean it had evaded the blockade. Every ship was assessed individually, including through a review of its papers, and some vessels could be allowed through for humanitarian reasons, the official added.

The official said the appearance of a vessel on US sanctions lists is not the only factor to make it subject to the blockade, adding that US forces are also closely monitoring some ships without taking action against them for operational reasons.

Centcom said in an update on October 13 that during the three months of the latest blockade, four commercial vessels had been disabled and 135 ships had been turned around by US forces.

The US military has turned around ships from Asia and also seized some tankers, previous Centcom statements said.

Washington has coupled its blockade with a sanctions campaign aimed at severing Iran's remaining financial links and depriving it of revenue. Last week, it imposed fresh sanctions on 17 vessels involved in transporting Iranian crude, petrochemicals and petroleum products.

A US Treasury spokesperson questioned shipping data suggesting vessels had evaded the blockade, saying ships could spoof their locations or use false identities when loading. Such data "should be taken with a grain of salt", the spokesperson said.

The Treasury spokesperson said Operation Economic Outcast, together with the blockade, was "suffocating the Iranian regime".

Torbjorn Soltvedt, principal Middle East analyst at risk intelligence company Verisk Maplecroft, said although there was no sign of Washington easing its blockade, worsening economic conditions in Iran could push Tehran to take greater risks.

"If Iran can move product tankers through, even in small numbers, jet fuel may be a good option. Iran's aviation industry is under increasing pressure from US sanctions, with a growing number of planes grounded, and a potential surplus of jet fuel at Iranian refineries," Soltvedt added.

Iranian crude exports fell to zero in September, according to Kpler, the first month without a shipment since the analytics firm began tracking the producer in 2013.

US Treasury Secretary Scott Bessent has said the blockade prevented most Chinese purchases of Iranian oil and left Iran unable to deliver crude to customers.