Two Americans teachers and an Indonesian national were killed and 10 others injured.

"The attack on these innocent victims, who were mostly school teachers, is an outrageous act of terrorism," the U.S. Embassy in Jakarta said in a statement Tuesday.

"We urge the government of Indonesia to take all necessary steps swiftly to apprehend and punish the perpetrators of this horrible attack."

The Indonesian government has condemned the attack and said it would do all it could to capture the perpetrators and bring them to justice.

The Indonesia military is calling for patience, however, citing extreme circumstances hampering the search for the perpetrators.

It has also brushed aside calls for an independent investigation into the attack which occurred on a road leading to a giant U.S.-owned gold and copper mine.

Papua regional military chief Major General Mahidin Simbolon told Reuters his troops were battling treacherous conditions in the search.

"Bear in mind this is a vast area with thick jungle, not to mention the heavy showers and thick fog which make it difficult to see and slippery," Simbolon said.

Some experts on the region are suggesting the Indonesian military itself might have been involved.

Australian academic and writer, Dr Denise Leith, told Radio New Zealand the OPM, a suspected separist group, would get very little benefit from the killings.

She said it was far more likely to have been the military who were involved.

"The military often create incidents to either justify its presence and an increase in military operations in an area or it will threaten foreign companies if they don't behave in a way the military are happy with," Leith said.