More than a dozen insurgent groups have been fighting the government for decades in Assam and neighbouring states of northeast India, killing thousands in attacks on civilians troops and paramilitary.
The groups blame the government of plundering the region's significant mineral and agricultural resources and ignoring demands for greater autonomy and greater economic opportunities.
But in an effort to ease tension and sway public opinion away from the militants, the Congress Party-led coalition government has held periodic talks with several of the groups, including the hard-line United Liberation Front of Asom (ULFA).
"The government always welcomes rebels back home. All differences can be settled through talks and understanding," said India's Home Minister P. Chidambaram, in his speech.
The more than 600 rebels in the Tuesday ceremony will reportedly receive government help to rebuild their lives.
More than 200 ethnic and tribal communities live in the country's strategic northeast made of eight mountainous states and circled by Bangladesh, Bhutan, China and Myanmar.
