As economic sanctions tighten around Iran, the Islamic Republic has turned to accepting alternative currencies as a way to receive payments for oil exports, the Financial Times reported on Monday.

The report focuses on a huge surge in gold exports from Turkey to Iran since March, the same time Iran was cut out of the SWIFT network, a global transaction system that handles payments for much of the petroleum industry, which forced Iran to seek alternative payment for its oil.

Although Turkey has reduced Iranian oil imports under EU and American pressure, Iran still provides 40 percent of Turkey’s petroleum, and between March and May, Turkey exported 58 tons of gold to the Islamic Republic, an increase of over 500%. According to the Financial Times, the gold exports were “sent in place of dollars for oil.”

Ugur Gurses, a financial analyst for the Turkish daily Radikal, said, “Iran converted $3 billion of its reserves into gold through financial operations with Turkey, bypassing sanctions.”

Speaking to Anadolu Agency on Monday, Turkish Energy and Natural Resources Minister Taner Yildiz denied that Turkey pays for Iranian oil by gold, saying that oil payments are made through existing agreements between private companies in dollars and lira.