Jakarta – A separatist group in Indonesia's Papua province claimed responsibility on Monday for a series of bomb attacks in the area and called for the closure of a controversial huge copper mine.

A small bomb exploded near the remote province's Timika airport on Sunday after two blasts on Friday near a mine operated by the local unit of US firm Freeport McMoRan Copper & Gold Inc.

No casualties were reported in the explosions and Freeport's operations were not disrupted.

Freeport's Grasberg mine – believed to have the world's third-largest copper reserve – has been a frequent source of controversy over its environmental impact and the share of revenue going to Papuans.

Kelly Kwalik, chief of the Free Papua Movement (OPM), issued a letter to members of the group urging them to take action to push for the closure of Freeport's mine. The letter was obtained by Reuters on Monday.

"I as the highest commander of the OPM with a brave heart issue this instruction for the closure of Freeport's mine because the presence of the company has been causing many problems leading to clashes among Papuan people," Kwalik said in the letter.

He wants the Papuan independence issue to be discussed during the United Nations General Assembly meeting this month. Kwalik told Reuters his group were responsible for the recent attacks.

Independence activists in Papua have waged a campaign for nearly 40 years to break away from Indonesia, while a low-level armed rebellion has also simmered, often related to disputes over the sharing of rich natural resources.

The Grasberg mine accounts for 40 percent of Freeport's total copper reserves of 93 billion pounds, according to the company's website. Freeport is the world's largest publicly traded copper miner. (Reporting by Telly Nathalia in Jakarta and Oka Barta Daud in Jayapura; Editing by Sugita Katyal)