According to the IMD, the epicentre of the quake, which struck at around 6:11pm, was located just over 60 kilometres northwest of the state capital Gangtok.
There is no electricity in Gangtok and Darjeeling. Telephone lines have also snapped in some parts of Sikkim; phone lines are jam-packed in West Bengal.
Tremors were felt in Delhi and many parts of north India. Reports of tremors also felt in Patna, Kolkata, Lucknow, Jaipur, Jharkhand and Guwahati.