Jakarta – Four people were wounded when troops opened fire with rubber bullets to break up a demonstration by thousands of protesters angered by the shooting of a man guarding a much-protested pulp and paper in North Sumatra, reports said Tuesday.

"It is calm there now, there is no more violence," a police spokesman said of the conditions in Porsea.

About 5,000 people attacked the Inti Indorayon Utama (IIU) pulp and paper plant four kilometres from Porsea on Monday after soldiers shot a 20 year old man the previous day, the Kompas daily said. As troops tried to stop the demonstration at least four people were wounded by rubber bullets, the daily said.

The deputy district police chief, Major Arif was injured in the clash in which the protesters damaged four cars, set 15 company trucks ablaze and vandalized or burned 23 houses and businesses, Kompas said.

IIU is under investigation by the government to determine whether it was causing environmental damage as claimed by the local population. Nearby residents have said the operation had not only denuded the forests in the area, causing erosion and a deterioriation of the water level in rivers but also polluted the waters with their waste. The company was causing air pollution and the plant emitted a strong smell which affected people in the area, they charged.

IIU has been the target of protests from locals and environmental watchdogs since it came into operation in 1989. The current investigation has forced the suspension of the plant's operation for three months.