Jakarta – Indonesian police were on standby to stem industrial unrest at three factories in a West Java city Saturday, a day after a pay dispute at Indonesia's largest polyester producer turned violent.

The day-long protest by some 4,000 factory workers in Purwakarta Friday erupted into the burning of some 30 cars and stoning of buildings when management fell short of meeting the workers' demand for a pay rise.

The workers at PT Indorama Synthetics, the largest polyester producer in Indonesia, asked for a monthly 150,000-rupiah (some 14 dollars) raise, while the management agreed only to a 25,000- rupiah (2.50 dollars) raise plus a 35,000-rupiah (3.50 dollars) additional allowance.

"We are securing three factories today. Indorama was quiet, but some 500 workers of Elegant (factory) are currently demonstrating and Indopanca (factory) workers are on strike," Sergeant Reno (eds: one name) from the Purwakarta police told AFP by telephone. Reno said the police have made no arrests so far.

Some 38 cars were attacked and set on fire by the angry crowd which also managed to damage the office and dormitory of Indorama employees, the Kompas daily reported. Nine rooms of the Rama International School in the compound were also damaged, and a fire truck that came to the location was attacked by the workers.

"Indorama has plenty of factories abroad, it is only fair to raise our income simply to buy rice," one demonstrator was quoted by the state-run Antara news agency as saying. Kompas reported that the average salary for the workers at the factory currently stands at 200,000 rupiah (18.50 dollars), above the minimum wage rate in the area.