DAMASCUS/LONDON: Iran has managed to export some liquefied petroleum gas and jet fuel despite a U.S. naval blockade that has brought its crude exports to a virtual standstill, according to shipping intelligence and people involved in maritime security.

At least eight gas tankers carrying Iranian LPG have left the Gulf of Oman since mid-July, according to analysis by U.S. advocacy group United Against Nuclear Iran, which monitors Iran-related tanker traffic using ship and satellite tracking.

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

The Iranian exports and the methods used to move the cargoes are being reported for the first time. While the shipments represent only a fraction of Iran's former energy exports, they provide rare evidence of petroleum products passing through a blockade that has halted Iranian crude exports.

Four maritime security experts who track Middle East oil movements said Tehran has been concealing such cargoes in recent weeks among a growing number of ship-to-ship transfers by other Middle East producers off Oman.

Six of the eight gas tankers and the jet-fuel tanker are under U.S. sanctions for transporting Iranian petroleum and petrochemical products, according to a Reuters analysis.

"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.

The LPG cargoes totaled an estimated 4.1 million barrels, Shelley said. Most sailed to Malaysia's Eastern Outer Port Limits for further ship-to-ship transfers, with likely destinations in China.

Shelley said the shipments were driven "more by opportunism" than evidence of a new Iranian strategy to export oil and petrochemicals using smaller vessels.

The U.S. military said its blockade was "ironclad" and cautioned that a vessel passing through did not necessarily mean it had evaded the blockade. A U.S. military official said ships are assessed individually, and some could be allowed through for humanitarian reasons.

U.S. Central Command said that during the three months of the latest blockade, four commercial vessels had been disabled and 135 ships turned around by U.S. forces.

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

The Iranian government did not respond to a request for comment.