Four suspected separatist rebels and a civilian have been killed in Indonesia's Aceh province where troops are in the fourth month of an assault on the guerrillas, the military said.

Soldiers shot dead two Free Aceh Movement (GAM) members in clashes in the Meureudu area of Pidie district on Monday, said military spokesman Ahmad Yani Basuki. Two other rebels were killed in two separate clashes in Pidie and Bireuen districts the same day, Basuki said.

Residents discovered a male corpse bearing severe torture marks in East Aceh on Monday.

Troops on Monday arrested a 26-year-old female rebel following a raid on a guerrilla base in the Gandapura area of Bireuen district, Basuki said.

Security authorities confiscated a 60-kilogram home-made bomb from the rebels after a raid in Aceh Jaya district.

Basuki also accused GAM of kidnapping four civilians including a 47-year-old woman in Central Aceh and Aceh Besar districts on Monday. The rebels could not immediately be reached for comment.

As of Monday, the military said 798 GAM rebels have been killed and 342 weapons seized during the operation that began May 19. It said more than 1,700 rebels have been arrested or surrendered, while 46 soldiers and 13 police officers have been killed.

Human rights activists and other groups have questioned whether the military figure for guerrilla deaths also includes civilians.

Aceh is under martial law as the military carries out its biggest offensive since the 1975 invasion of East Timor.