The 275-meter tanker started offloading its cargo into a refinery owned by Cia. Espanola de Petroleos, near Algeciras, a few miles from Gibraltar, according to Bloomberg Business.

As the Monte Toledo started to pump to shore through two 21-inch floating hoses connected to a giant buoy and a 1.8-kilometer submarine pipeline, Iranian President Hassan Rouhani declared in Tehran that more oil exports “will be added soon.”

Around Europe, other tankers with Iranian oil are close behind the Monte Toledo. In February, 29 vessels loaded crude from the Middle Eastern nation, according to data compiled by Bloomberg. Of them, three are heading toward Europe -- the Eurohope tanker is sailing to Constanta, an oil port in Romania, and the Atlantas is on its way to France. Another one, the Distya Akula, is anchored at the mouth of the Suez Canal, and is likely to head into a Mediterranean port.

The Monte Toledo and its companions are the vanguard in the return of Iran into the European oil market. Petro-Logistics SA, a Geneva-based tanker-tracking firm, estimated Iran exported in February about 1.4 million barrels a day, up 350,000 barrels a day from the average 2015 level.

Seth Kleinman, head of energy research at Citigroup in London, was quoted saying that in addition to higher export volumes this month, more countries were buying.

"You see tankers going to Spain, Romania, Tanzania, France and the U.A.E. You got an uptick to India in February too," he said.

Before the embargo Europe imported on average about 400,000 barrels a day of oil from Iran, according to the International Energy Agency.

Iran plans to boost its production back to the 3.6 million barrels a day it pumped in 2011, the report said.