A supertanker with Iranian crude is heading toward Poland’s Baltic Sea port of Gdansk, trade sources said and ship-tracking data showed, as Iran continues to claw back market share after the lifting of Western sanctions.

It was not immediately clear whether the buyer was Polish refiners PKN Orlen or Grupa Lotos, or whether the oil would remain in Poland or be shipped to Germany, which is connected by pipeline to Gdansk.

Regardless of the ultimate destination, the cargo is the first Iranian crude sold into this part of the Baltic Sea market since January’s lifting of sanctions, intensifying the battle for market share between top producers including Russia and Saudi Arabia.

The Atlantas Very Large Crude Carrier (VLCC) left Iran’s main oil export terminal Kharg Island laden with 2 million barrels of crude on June 27, Reuters ship tracking showed, and is destined for Gdansk.

VLCCs cannot dock in the Baltic Sea port but sources said the oil would be transferred to a smaller vessel to discharge in Gdansk.

Nearly wholly dependent on oil from Russia, Polish refiners are taking advantage of the turf war and cheap oil prices to try alternative grades and gain a stronger negotiating position with Russian producers.

Lotos started taking Saudi oil last year – in a development that Moscow called a major challenge – and PKN Orlen recently signed a supply deal with Saudi Aramco, its first long-term deal with a supplier from the Gulf region.

Both companies said they were also interested in running Iranian oil in their refineries.

Saudi Arabia has been aggressively expanding its global buyer list and Iran has been hot on Riyadh’s heals in its efforts to get its old customers back and find new ones. Oil major Shell resumed Iranian oil purchases this month.

Tensions between the two Gulf producers have stymied OPEC’s attempts to find a plan to boost global oil prices.

Before sanctions, Iran was exporting about 2.2 million barrels per day (bpd). July exports are expected to be around 2.1 million bpd, up about 70 percent year-on-year.

In May, Poland’s deputy energy minister said the country was in talks with Iran over cooperation in the oil and gas sector.