JAKARTA/TIMIKA, Indonesia (Reuters) - An Indonesian police officer was killed and a second wounded on Wednesday, after both were shot in the back in an area near Freeport-McMoRan Inc s giant Grasberg copper mine in the eastern province of Papua, police said.  The officers were patrolling an area close to where a Freeport vehicle was targeted in a shooting on Tuesday, Papua police spokesman Suryadi Diaz said in a statement. A helicopter flew the men to a hospital in the nearby lowland city of Timika. The main access road to Grasberg remained closed, Freeport Indonesia spokesman Riza Pratama said, referring to a 79-mile (127-km) stretch from Timika to the mining town of Tembagapura that runs near a river rich with gold tailings from the mine upstream. A string of at least 15 separate shooting incidents in the area since mid-August that wounded at least 12 people and killed two police officers has been blamed by police on an  armed criminal group , but linked to separatist rebels by others. In a statement, the separatist West Papua National Liberation Army (TPN-OPM), a group linked to the Free Papua Movement, claimed responsibility for Wednesday s incident. The group has said it is at war with police, military and Freeport. For decades, there have been sporadic attacks along the road where the shootings took place, but authorities  efforts to catch the perpetrators have been hampered by thick surrounding jungle.  The Indonesian Military (TNI) and police have urged the Armed Separatist Movement in Papua to surrender, but until now no one has turned themselves in,  Indonesian military chief Gatot Nurmantyo said in a statement.   Armed separatists cannot be left alone,  he said, adding that reining in such activities was the domain of the military, which was preparing  emergency measures  in case persuasive approaches by the police and military failed. Papua has had a long-running, and sometimes violent, separatist movement since the province was incorporated into Indonesia after a widely criticised 1969 U.N.-backed referendum. Foreign journalists have in the past required special permission to report in Papua, and once there, have had security forces restrict their movement and work. President Joko Widodo has pledged to make the region more accessible to foreign media by inviting reporters on government-sponsored trips, although coverage remains difficult. 