Turkey, a major buyer of oil and gas from Iran, will no longer give a breakdown of where its energy imports come from, an official at the country's statistics office said Friday.

The move, as the West tightens sanctions on Tehran over its contested nuclear programme, follows a request from Turkey's refining monopoly TUPRAS which already bars the Turkish Statistics Institute (TUIK) from detailing its oil imports.

"TUPRAS asked us last month not to reveal the origin of our crude oil imports and instead give an overall figure," a TUIK official told AFP, requesting anonymity.

"We were not informed of the reason for the change in policy," he said.

TUPRAS declined to comment on the issue.

Fearing that Tehran aims to acquire nuclear weapons, the United States has led Western powers to impose ever tougher sanctions against Iran which rejects the charge outright, insisting its programme is for peaceful purposes only.

Under a law approved last year, Washington threatened to penalise foreign financial institutions over transactions with Iran's central bank, which handles sales of the country's key oil and gas export.

On November 30, the US Senate unanimously approved new economic sanctions aimed at further crippling Iran's energy, shipping and port sectors but shortly thereafter, the government extended exemptions from the sanctions to nine major economic powers, including Turkey, China, Taiwan, India and South Korea.

Ankara in return has cut its Iranian oil purchases by 20 percent. Energy Minister Taner Yildiz said last month Turkey met half of its crude oil needs from Iran in 2011 but was now trying to source more from Libya, Saudi Arabia and Russia.

The European Union has imposed similar sanctions against Iran.