By Aaron Sheldrick

TOKYO, May 31 (Reuters) - The four biggest buyers of Iranian crude oil in Asia increased their imports in April by nearly 23 percent from a year earlier as Tehran's exemption from a global production cuts favours the country's oil export drive.

China, India, South Korea and Japan imported 1.6 million barrels per day (bpd) last month, government and ship-tracking data showed.

However, exports to Asia were down nearly 18 percent from March, suggesting Iran may be at the limits of its efforts to boost production after sanctions were lifted in January 2015. Iran has cleared out most of the oil it held in storage while the sanctions were in place. Asian countries buy most of the oil the country exports.

Iran is pushing hard to raise production and hopes to sign deals with oil majors such as Total and Lukoil this year after the re-election this month of President Hassan Rouhani.

A tender for the Azadegan oilfield, which has an estimated 37 billion barrels of crude, started on Monday, the Islamic Republic News Agency reported.

The development of new fields as well as improved oil recovery from mature reservoirs should allow Iran, the third-largest producer in the Organization of the Petroleum Exporting Countries (OPEC), to have the capacity to pump 5 million barrels per day (bpd), or 5 percent of global crude, from 4 million bpd now.

In the first four months of 2017, the four Asian countries imported 1.8 million bpd, a 40 percent rise from the same period last year.

Iran was exempted from a deal between OPEC and other producers, including Russia, to reduce output by 1.8 million bpd from Jan. 1, and will remain so after the cut was extended last week for a further nine months.

Japan's trade ministry on Wednesday released official data, showing Iranian imports were at 41,401 bpd last month, more than double the figure from a year earlier.

They were down sharply from more than 220,000 bpd in March as Japanese buyers waited for the government to extend a state-backed insurance arrangement for purchases.

Tanker tracking data on ThomsonReuters Eikon indicates more oil was scheduled to arrive in Japan in April but importers are allowed to hold cargoes offshore or in warehouses before clearing them, under government regulations.



The following tables show Asia's Iran crude imports in bpd for last month and the year to date.

Country Apr-17 Apr-16 yr/yr pct China 641,084 671,176 -4.5 India 535,100 392,900 36.2 Japan 41,401 19,161 116.1 South Korea 403,700 237,133 70.2 Total 1,621,285 1,320,370 22.8 Country Jan-Apr 2017 Jan-Apr 2016 yr/yr pct China 579,582 551,282 5.1 India 563,800 322,500 74.8 Japan 176,183 162,588 8.4 South Korea 490,342 247,628 98.0 Total 1,809,907 1,283,998 41.0



(Reporting by Aaron Sheldrick; Editing by Vyas Mohan and Christian Schmollinger) ((aaron.sheldrick@thomsonreuters.com; 81-3-6441-1320; Reuters Messaging: aaron.sheldrick.thomsonreuters.com@reuters.net))