New Delhi  - Twelve tribal rebels were killed in a clash between two groups in India's north-eastern Nagaland state on Wednesday, news reports said.

Heavily armed militants belonging to two factions of the rebel National Socialist Council of Nagaland (NSCN) fought each other with rifles and guns early Wednesday near the village of Keloshe, about 15 kilometres from Dimapur, the commercial hub of Nagaland, IANS news agency reported citing the police.

Twelve persons were killed and one injured in the clash which continued for four hours, the police said.

"Clashes broke out between the NSCN's Isak-Muivah (NSCN-IM) faction and the NSCN-Unification (NSCN-U)," Liremo Lotha, police chief of Dimapur, was quoted as saying.

The police said they were not aware of the immediate reason for the clash but that the two groups had been struggling for territorial supremacy in the area for some time.

Twelve militants were killed in a similar battle between the two groups in the same area on May 16.

More than 50 rebels have been killed in such inter-faction battles since early March, the police said.

The Isak-Muivah faction of the NSCN entered a ceasefire agreement with the Indian government in August 1997 and is currently engaged in peace negotiations. The NSCN-U does not have a ceasefire pact.

Nagaland has witnessed one of the longest-running insurgencies in India that began in the 1950s. Most of the rebel groups are fighting for an independent land for the Nagas or for greater autonomy.

An estimated 50 militant groups operate in the north-eastern Indian states of Assam, Arunachal Pradesh, Nagaland, Tripura, Mizoram, Manipur and Meghalaya. (dpa)