The tremors were felt at 2.26 p.m. No casualties were reported immediately.
The epicentre was plotted along the India-Bhutan border, 125 km northwest of Guwahati.
Preliminary reports say cracks developed in apartments and concrete structures in Guwahati.
This is the fifth and the highest intensity earthquake to have rocked the northeast since Aug 13, according to the Regional Seismological Centre of Shillong.
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