"Prices have risen again and the culprit is the cooperatives. Supply is tight because the cooperatives do not have enough trucks to transport cooking oil to the markets," said one trader in Jakarta.

Traders said ex-factory olein was quoted at 5,100-5,150 rupiah/kg in Jakarta against 5,000 rupiah/kg at the close on Thursday.

Some traders said the market cooperative group (Inkoppas), which had been assigned by the Bulog commodity regulator to distribute cooking oil, still sold olein at 4,500-4,750 rupiah/kg to retailers.

The government has intended to stabilise prices at between 3,900-4,000 rupiah/kg in the traditional markets.

Traders said they largely ignored rumours of possible riots ahead of the independence day on Monday.

"The fact is that I am still here in Jakarta. Iknow many people, including Chinese traders, have left the country but it is because of the long holiday and also because they have money," said one trader.

"I will work on Saturday, as usual," he said.

Bulog said it planned to buy crude palm oil (CPO) in addition to olein from private companies and state-run plantations to further enhance supply in the market, the official Antara news agency reported on Friday.

It quoted Bulog chairman Beddu Amang as saying on Thursday the CPO would be bought through a tender starting next week and that it would be processed into olein, which is used as cooking oil, in Java.

Amang said supply was not smooth because of difficulties in finding ships to transport olein from Sumatra, where most of the refiners are, to the main island of Java.

Antara said the market cooperative group also had trouble finding trucks.

Amang said at least 70,000 tonnes of cooking oil was waiting for transportation to Java from Sumatra. He said Bulog would buy cooking oil on a C&F basisrather than FOB because of difficulties in finding ships.

Antara gave no further details.

Bulog bought 137,575 tonnes of cooking oil through three tenders in July and August with a total value of 650 billion rupiah in an effort to stabilise prices.