Riot police fired water cannon to break up the violent demonstration by about 1,000 stone-throwing protesters who threw Molotov cocktails, smashed police cars and tried to break down the gates of parliament on Tuesday.

'Some sixteen protesters were arrested during yesterday's demonstrations and they are under police investigation,' police spokesman Abu Bakar Nataprawira told reporters.

He said the student organisations that organised the rally had been infiltrated by 'another group,' a possible reference to opposition political agitators whom the government accuses of stoking street violence.

Mr Mallarangeng said protesters had a right to express themselves peacefully but accused Tuesday's demonstrators of being politically motivated.

'The president and the government have always seen any protests as the flower of reform. But in any democratic country protesters must respect the law and they mustn't be violent,' he said.

'We're afraid that this protest is politically motivated. There must be many groups that want to profit from the situation for their political interest.'

Student anger at the treatment of the protesters, one of whom died in hospital last week after being beaten by police in an earlier protest, is likely to increase after a police car ran down a protester on Tuesday.

Television footage showed the car apparently swerving to hit the young man as demonstrators pelted police vehicles with rocks, throwing him into the air.

Mr Nataprawira defended the officers involved, saying: 'The police had no other choice but to hit the protester as the crowd was starting to pelt the car with stones. It was just a move to defend themselves from the protesters that had destroyed several police vehicles.'

Last month's price hike has triggered protests throughout the archipelago but a government scheme to offer cash compensation and free rice to the poor helped dull public anger.

Indonesia's May inflation rate rose into double digits for the first time in nearly two years as the higher fuel prices rippled across the economy.

The consumer price index jumped 10.38 per cent in May from a year ago and by 1.41 per cent from April, its fastest pace in 20 months.

The year-on-year inflation rate is the sharpest since September 2006, when the CPI rose 14.55 per cent. -- AFP