Fuel smuggled from rebel-controlled areas in Syria could slow the growth of Turkey's own fuel market by as much as 3%, BP Turkey manager Martin Thomsen has said.
"The smuggled fuel coming from Syria has begun to affect us adversely since the beginning of April," Thomsen told reporters.
"Fuel sales have remarkably dropped, particularly in southern provinces," he added.
Turkey's fuel market was expected to grow between 4% and 4.5% in 2014, but the rise of illicitly smuggled fuel from Syria to Turkey could shave 1.5 to 3 points from expectations, Thomsen said.
While the overall volume of fuel being smuggled from Syria to Turkey is almost impossible to track, Turkish daily Hurriyet reported that it has reached around 500,000 tons, citing industry sources.
Licensed distributors sell gasoline at 4.5 liras per litre, while the equivalent can be purchased at the Turkey-Syria border for 1.1 liras per litre, Thomsen said, adding that smuggled fuel has reached provinces far from Turkey's 559-mile border with Syria.
"The market has been affected in a triangle-shaped region up to Central Anatolia," he said.
Gas station operators in Turkey have held crisis meetings in which they have complained about the new source of cheap fuel reaching Turkey but the trade continues unabated.
While some groups have struck a deal to sell oil and fuel to the Syrian government, other fuel has been sold outside the country.
The Islamic State (IS) which is holding 49 Turks hostage, controls all of Syria's major oil fields after it seized the Tanak oil field in early July.
IS, formerly known as Isis, the Islamic State of Iraq and al-Sham, had previously seized control of the major al-Omar oil field in Syria, but smaller oil facilities remain in the hands of local tribesmen, a monitoring group reported.