OPEC' oil output continues to increase in April, gaining larger world market share, the oil cartel's monthly report said on Friday.

"Total OPEC crude oil production in April averaged 32.44 mb/d, an increase of 188 tb/d over the previous month, crude oil output increased mostly from Iran and Iraq," the report said.

It was the second consecutive month that the Organization of Petroleum Exporting Countries (OPEC) increased its oil output under the pressure of the low oil price market. Iran has become the main thrust of the increase of the cartel's crude production.

Benefited by western states sanction relief, Tehran' oil output has increased from 2,837 thousand barrels per day in the year 2015 to 3,451 thousand barrels per day in April, and it still has the capacity to pump more crude in the next months.

Meanwhile, OPEC sees the trend of decline of its rivals' oil supply.

"Non-OPEC oil supply for 2016 is forecast to contract by 0.74 mb/d, seeing a minor downward revision of 10 tb/d from the previous report, to average 56.40 mb/d," OPEC said.

"The share of OPEC crude oil in total global production increased to 34 percent in April compared with the previous month," the cartel reported.

The production cut has been a key issue in keeping the balance of the oil market since the oil price collapsed, however, world's major oil producers fail to make a substantial agreement over the issue.