The vessel, called Faxon, docked at the Puerto la Cruz refinery in eastern Venezuela in the Thursday evening after the Venezuelan Navy said it escorted the fourth tanker bringing Iranian fuel through its waters, according to Reuters.

Previously on the same day the Petunia tanker, the third one, arrived at the El Palito port in western Venezuela, military officials announced, and a fifth tanker Clavel is expected in the coming days.

The first ship, Fortune, had anchored on Tuesday at El Palito. The port’s refinery is able to process 140,000 barrels of oil a day.

The second tanker, Forest, arrived at the Paraguana refinery complex in northwestern Falcon state on Wednesday, Oil Minister Tareck El Aissami said on Twitter.

The Paraguana refinery, the largest in Venezuela and one of the largest in the world, can process 950,000 barrels of fuel per day, but its production has plummeted alongside the country’s crude supply.

The tankers “bring fuel, additives and spare parts, among other equipment, to increase our capacity for refining and oil production,” El Aissami said Monday.

Secretary of Iran’s Supreme National Security Council Ali Shamkhani paid tribute to the crew of the oil tankers that have carried fuel to Venezuela for humiliating the US sanctions in the global arena.

In a message on his Twitter account, Shamkhani said the flag of Iran continues to be raised in the world thanks to the endeavors and mettlesome action by the Iranians that have devoted themselves to serving the country and are not afraid of the enemies.

The US has closely monitored the shipments, concerned that Iran and Venezuela were taking their longstanding ties to a new strategic level.

Washington has said it is weighing a response to the shipments.

The oil industries of Iran and Venezuela are both under US sanctions. Iran is providing its fellow OPEC member up to 1.53 million barrels of gasoline and refining components to help ease an acute shortage, the result of the near-complete breakdown in its refining network as well as the sanctions.

Venezuela has been in recession for six years, its economy in shambles and its citizens struggling with shortages of basic necessities such as food and medicines.

US sanctions have targeted Venezuelan oil exports, starving Caracas of vital income.

Venezuela is almost entirely dependent on its oil revenues but its production has fallen to roughly a quarter of its 2008 level.

Venezuelan President Nicolas Maduro’s government blames that on US sanctions, including against state oil company PDVSA.

Falling oil prices since 2014 have exacerbated Venezuela’s economic crisis.

Venezuela has the world’s largest proven oil reserves, but its capacity to refine crude into gasoline is limited.

AFP and Tasnim News Agency contributed to this story.