Iran has secretly resumed delivery of oil to Syria’s Assad regime, desperately in need of fuel, according to firms tracking maritime shipments.

A delivery of about one million barrels of crude was made at the Mediterranean port of Baniyas in western Syria in the first week of May, according to TankerTrackers.com and ClipperData.

The shipment is the first this year from the Islamic Republic, which has propped up the Assad regime economically since the start of the Syrian uprising in March 2011.

Facing its own difficulties amid US sanctions, Iran cut off lines of credit worth billions of dollars to the Assad regime last autumn.

Tehran also has faced the challenge of getting oil to Syria, as the US stepped up pressure. The Assad regime claims Egypt blocked movement through the Suez Canal, although Cairo’s El-Sisi Government has denied the allegation.

The loss of Tehran’s oil — estimated at one to three million barrels a month — has led to gasoline shortages in regime-held areas of Syria, with drivers queueing for hours at petrol stations.

See also Syria Daily, April 30: Residents Endure Oil Crisis Amid “Corrupt and Unjust People in Charge”

Iran’s official oil exports have fallen almost 60% since April, falling from 2.5 million barrels per day to 1.1 million bpd.

But analysts say Tehran could be moving up to another 400,000 bpd through “off the grid” shipments, as tankers turn off transponders and covertly off-load.

A Secret Shipment

Tracking companies said an Iranian Supermax tanker, previously known as True Ocean, caught their attention with a series of unusual moves. Now traveling as the Masal, the tanker is on the US Treasury’s list of vessels bringing oil to Syria in the past.

The Masal left Iran in March heading towards eastern ports of Turkey. It anchored for three weeks before leaving the port of Iskenderun, still carrying a million barrels of oil.

Then the tanker switched off its transponder as it neared the Syrian shore, and did not come back online until May 7 as it returned to Iran.

ClipperData says the Masal is the second ship carrying Iranian oil that has gone dark in the Mediterranean since April.