The Centre on Wednesday directed the Assam government to nab the "ring leaders" involved in ethnic violence in the state but ruled out a Bangladeshi hand in the trouble which so far has claimed 40 lives.
Union Home Secretary R K Singh also said 2,000 central security personnel have been deputed to guard Guwahati-bound trains and railway tracks which were disrupted.
"We have asked the state government to book ring leaders of both sides so that violence can be checked immediately. No one involved in the violence will be spared," Singh told reporters.
Asked about claims that some people involved in the clash might have links with neighbouring Bangladesh, Singh ruled out the possibility of involvement of anyone from across the border.
"The international border is sealed. It is simply impossible for any organised group crossing over to India from across the border to carry out the attacks," he said.
He said 1,000 paramilitary personnel and 1,000 Railway Protection Force personnel have been deputed to guard Assam-bound trains and tracks for smooth running of trains to the northeast.
Singh said 2,500 paramilitary personnel have reached Assam to assist the local administration while 2,300 more men will reach the state tonight.
"Another 15 companies (1,500 personnel) are on their way," he said.