The veracity of the video is yet to be ascertained.
Police said two militants came on a motorcycle and lobbed a grenade at a crowded place in Bokolia, a small township.
A red alert was triggered in Jorhat district following information about ULFA militants entering the district.
The explosion comes two days after a powerful bomb was defused near the NH 37 at Haldapara in Goalpara district.
Bangladesh has launched a major crackdown on ULFA militants.
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