Japan cut oil imports from Iran by 65 percent in April while boosting shipments from Saudi Arabia, official data showed Wednesday, amid Western efforts to squeeze Tehran over its atomic programme.

Resource-poor Japan, which relies heavily on Middle East oil, came under pressure earlier this year to curb imports from Iran, with Washington seeking to push Tehran into a corner over what it says is a nuclear weapons programme.

In March Japan pledged to further cut its Iranian oil imports, which it said had already shrunk by 40 percent over the past five years.

On Wednesday, the trade data showed Japan imported 564,962 kilolitres of Iranian crude oil in April, or about 118,450 barrels a day, a drop of 65.5 percent from the same month a year earlier.

The figures -- the first full month of data since Tokyo won an exemption from US sanctions against doing business with Iran -- also showed imports from Saudi Arabia jumped 36.4 percent in the same month to 6.58 million kilolitres.

That is about about 1.38 million barrels a day.

Japan and China are Tehran's biggest oil customers, alongside India and the European Union.

Earlier this month, Iran's state-run oil company denied that China and Japan had sharply cut imports of Iranian crude, echoing Tehran's insistence that Western economic sanctions were having little effect.

The United States said it was exempting 11 countries, including European Union members and Japan, from punitive measures on Iran while praising them for reducing dependency on oil from the country.

In exchange for the reduction, Tokyo won concessions that would exempt its financial institutions from sanctions on banks that do business with the central bank in Iran, which generally handles oil purchases.

The European Union is poised to fully implement an embargo on Iranian oil from July 1.

That could complicate future Japanese imports as the Asian nation's oil firms usually buy insurance domestically for crude shipments, but most of that insurance is sold into European reinsurance markets.

With all of its nuclear reactors now switched off in the wake of the March 2011 quake-tsunami disaster and ensuring atomic crisis, Japan is heavily dependent on fossil fuels to make up an energy shortfall.