They shot dead 13 persons in a daredevil attack in a market place in the North Eastern state.
The figure of those who died went up to 14, after another injured person succumbed later.
The terrorists linked to the outlawed National Democratic Federation of Bodoland or NDFB-S undertook the attack, said police sources.
There were images of smoke billowing out of shops that caught fire and that of gun-toting terrorists.
The attack took place in Balajan Tiniali, which is nearly 215 km from the capital, Guwahati. The attackers had come in an auto-rickshaw, began indiscriminate killing and escaped. Just one of the terrorists got killed in retaliatory fire while others managed to escape.
After the incident, Home minister Rajnath Singh spoke to NSA Alert has been sounded in North East India, especially, Assam. NDFB is a Bodo group that has been involved in extremist acts in Assam for many years. It has been fighting for a separate Bodo state or a republic.
The group has a cadre of over 1,000 armed separatists. It is a separatist group that is heavily armed and has killed hundreds in Assam over the last several years. It has killed non-Assamese including Hindi speakers, Muslims and outsiders in Assam.