The Organization of the Petroleum Exporting Countries (OPEC) formally declared on Wednesday to immediately raise its quota by 500,000 barrels per day (bpd) to rein in soaring oil prices.

"The conference decided to increase the production ceiling to 27.5 million bpd immediately," said a final statement issued at the end of the OPEC's ministerial meeting held in the western Iranian city of Isfahan.

The oil bloc also decided to authorize the cartel president to raise an additional 500,000 bpd increase if the prices remain at the current levels or continue to rise, added the statement.

In addition, the statement said the increase decision was a "reaffirmation" of the cartel's commitment to ensuring adequate oil supplies consistent with robust economic growth.

Expecting another year of strong global oil demands, OPEC members also agreed to accelerate expanding their production capacity and invest more in new oil well exploration and refining facilities.

Promising to take appropriate and prompt action to the market demand, OPEC member states decided to hold its next meeting on June 7.

Delegates from 11 members of the cartel, including Iran, Algeria, Indonesia, Kuwait, Saudi Arabia, Iraq, Libya, Qatar, the United Arab Emirates, Venezuela and Nigeria, and some non-OPEC countries, including Oman, Angola, Mexico and Syria, were present at the key conference.

The meeting opened as soaring prices raised global concerns over oil supply. Futures prices reached 55.65 US dollars a barrel in New York last week and lingered around 55 dollars a barrel thereafter.