Tim Dodd, Jakarta – Security problems are worsening at the giant Freeport copper and gold mine in Indonesia's Papua province after soldiers guarding the facility discovered a bomb under a bridge on the mine's only access road on Saturday.

According to local police commander, Superintendent Sumarjiyo, the bomb, which did not explode, was discovered about the same time as unknown gunmen opened fire on Indonesian troops on a nearby section of the same road, wounding one soldier.

The two incidents on Saturday after came two weeks after three teachers from the local international school, including two Americans, were shot and killed on the same road in inaccessible, mountainous country.

The discovery of the bomb takes the security threat to Freeport to a new level because the mine's entire production of copper and gold is piped to the coast, in slurry form, in a highly vulnerable pipeline running next to the road.

Sumarjiyo said yesterday that seven of his men saw the bomb after it was discovered by security troops from Battalion 515. He said that "there must be a connection" between the bomb and the two shooting incidents.

Earlier, Papua's military commander Major-General Mahidin Simbolon was reported to say that the bomb was made from materials belonging to Freeport. Freeport's spokesman could not be contacted for comment yesterday.

The Indonesian military has blamed the Free Papua movement (OPM) for the shootings while human rights groups have cast suspicion on the military for being behind the incidents. The mine, which had the world's largest reserves of copper and gold, is majority owned by Freeport McMoRan Copper and Gold. Minority shares are held by Rio Tinto and the Indonesian government.