The first of five Iranian tankers carrying fuel to Venezuela has moored at a port serving the South American country's El Palito refinery, the nation's oil minister said Monday, and Refinitiv Eikon data showed a second vessel had entered its waters.

Iran is providing Venezuela with 1.53 million barrels of gasoline and refining components in a move criticized by US authorities as both countries are under US sanctions, according to the governments, sources and calculations by TankerTrackers.com.

Refinitiv Eikon data showed that the tanker Fortune docked at one of El Palito's berths around 1 a.m. local time (0500 GMT).

A second vessel, the Forest, entered Venezuelan waters and was being escorted by the country's military on Monday morning, according to the Eikon data and Venezuela's navy. A third tanker, the Petunia, was approaching the Caribbean, according to the data.

Tareck El Aissami, Venezuela's economy vice president and recently named oil minister, posted photos on Twitter of the Fortune arriving.

"We continue advancing and overcoming," El Aissami wrote.

A senior Trump administration official said earlier this month that Washington was considering a response to the shipments. A Pentagon spokesman said last week he was not aware of any military move planned. The first two vessels did not appear to face interference.

Neither the White House nor the US State Department immediately responded to requests for comment on Monday, an American holiday.

Venezuela is suffering acute gasoline shortages due to the near-collapse of its 1.3 million barrel-per-day refining network after years of underinvestment and mismanagement, as well as US sanctions aimed at ousting socialist President Nicolas Maduro.

Venezuela's refining network in May increased its joint crude processing rate to about 215,000 barrels per day (bpd) from 110,000 bpd in March, following the arrival of spare parts supplied in flights by Iran's Mahan Air, according to three people familiar with the matter, who spoke on condition of anonymity.

The 146,000-bpd El Palito refinery is now in the process of restarting its fluid catalytic cracker, a key unit for finished fuel production, one of the people said.

The 187,000-bpd Puerto la Cruz refinery, which serves Venezuela's eastern region, remains out of service, the people said.

Venezuelan officials have portrayed the arrival of the gasoline as a victory over US sanctions.

Washington and Venezuela's opposition, which argue that Maduro is usurping power since rigging his 2018 re-election, say the gasoline will likely be available only to security forces and well-connected individuals.