"The tender of the new nine oil and gas fields is expected to take place in October, after we secure contracts from the previous round of tenders," Ministry of oil and gas Director General Iin Arifin Tachyan told the daily Jakarta Post on Monday.

The government earlier this year offered 11 oil and gas field concessions and the next nine are located in Papua, East Kalimantan, South Sulawesi, Natuna Island and offshore Java.

Iin said the tenders would be closed at the end of July and the winners would be announced in August.

Iin also said the government was considering incentives for investors by increasing the production split to induce more investment in the sector.

Under existing production-sharing contracts, investors are entitled to take 15% of their oil output and 30% of their gas output. The remainder goes to the government.

Iin said in the earlier offering that the government had already increased the oil split for investors to between 20% to 25%, and to 35% for gas.

The oil and gas sector has been the main source of income for the government for the past 30 years.

Last year, 29% of the government's income came from this sector, where investors spent between $US5 billion and $US6 billion on exploration and production activities, or about 40% of total investment in the country during that period.

However, due to various uncertainties at home and overseas, investment in the oil and gas sector has started to decline. The government only signed two new contracts last year.

Industry experts have said though Indonesia is rich in hydrocarbon deposits, it is still an unattractive investment due to its many problems.