Around 242 tribal guerrillas of mountainous southern Assam laid down their huge cache of arms and ammunition in different phases to the security forces during the past three weeks ending three decades of terrorism in three northeastern states - Assam, Mizoram and Tripura, officials said on Tuesday.

Disclosing this to media, the officials of Assam Rifles and Assam police said in Karimganj that 242 local tribal militants of various local outfits in different phases surrendered to the Assam Rifles and Assam police in Karimganj and Hailakandi districts in southern Assam since December 8. 

The ultras, belonging to various Reang tribal (a primitive tribe) outfits, deposited 150 various types of fire arms and huge cache of ammunition. These include four AK series Rifle, one Chinese rifle, three M-20 pistols and 110 assorted weapons.

"The police and district authorities are holding a series of talks with these militants during the past three years. As part of the ongoing talks, the rebels deposited their arms and returned to the mainstream. Their violent and criminal activities were also stopped," a senior Assam police official said refusing to be identified.

The official said that the militants are infrequently conducting violent and criminal activities including kidnapping in Mizoram, southern Assam and northern Tripura for the past one decade. 

"A validation process of the extremists was held by the Assam Rifles and Assam police on Monday and Tuesday in Karimganj. Before their rehabilitation, a formal surrender ceremony would be held soon," the official said. 

Assam shares borders with six northeastern states - Mizoram, Tripura, Manipur, Meghalaya, Nagaland and Arunachal Pradesh.