After days spent denying the gasoline the US seized last week came from Iran, officials from the Islamic republic reversed course on Monday.

Iranian Oil Minister Bijan Namdar Zanganeh admitted at a briefing in Tehran that the 1m-plus barrels of oil confiscated were in fact headed from Iran to Venezuela, Bloomberg reports.

"The cargoes were loaded from Iran, but neither the ships nor the cargoes belonged to Iran, and the US declared victory for itself in the middle of this," Zanganeh reportedly said.

"The fuel was Iranian, but it had been sold to Venezuela and its payment had been cleared."

After the news of the seizure broke last week, Iran’s ambassador to Venezuela Hojat Soltani said it was "another lie and act of psychological warfare perpetrated by the US propaganda machine".

Pirates of the Caribbean

Soltani's message was echoed on Saturday by Foreign Minister Javad Zarif, who tweeted that "'Pirates of the Caribbean' have their own judges and courts now", implying the US had engaged in piracy in having the cargo seized in its courts last month.

"Sadly for them, stolen booty wasn't Iran's. Fuel was sold [free on board] Persian Gulf. Ship and flag weren't ours either," Zarif said on the social media site.

He added that it was "hollow, cheap propaganda" to deflect from the US failure to convince the UN Security Council to extend an arms embargo on Iran indefinitely. China and Russia, two of the council's five, veto-wielding permanent members, voted against the measure last Friday.

The same day, reports began circulating that the US had seized Iranian gasoline off four Liberian-flagged, Greek-linked tankers.

Ship-to-ship

Details on the seizure are still scant, but media reports citing US officials suggest the cargo was removed from four product tankers — the 37,400-dwt Bella (built 2000), 47,400-dwt Bering (built 1998), 46,200-dwt Pandi (built 1996) and 37,300-dwt Luna (built 2000) — with the consent of the ships' owners in a ship-to-ship transfer.

On Friday, officials reportedly said the gasoline was en route to Houston.

The registered owners of the Bella, Bering, Pandi and Luna are reportedly linked to Greek firm IMS, which had one of its managed ships, the 8,055-dwt Wila (built 1997), boarded by Iranian forces on Wednesday.

Maritime security consultancy Dryad Global suggested the move was retaliation for the failure of the quartet to complete the voyage.

The ships had also reportedly withdrawn from a flotilla of five Iranian-flagged product tankers that delivered gasoline to Venezuela in late May and early June under threat of US sanctions.

The US has tightened the vice on both countries in recent years in an attempt to sever their strengthening trade ties and topple their ruling governments.