Over a hundred people have been injured in the 6.8 magnitude temblor which has caused extensive damage to buildings and roads in Sikkim and several other places.
The casualties have occurred mostly in the North District and in towns and villages like Rangpo, Dikchu, Singtam and Chungthang located along the course of Teesta river, they said.
In Gangtok, power was restored this morning. Residents had spent the night outside their houses fearing aftershocks.
At least 20 aftershocks throughout the night had created panic in the city. Rescue teams have been dispatched to various affected areas this morning, the officials said. The toll in Sikkim till last night was seven.
In West Bengal, the toll rose to five with reports reaching Kolkata saying that two deaths have occurred in Kalimpong area in Darjeeling while one person each was killed in Siliguri and Jalpaiguri areas and one in a tea garden in Doors.
Chinese state-run news agency Xinhua reported that at least seven persons have been killed and 22 others injured in Tibet in the quake which has caused landslides and has disrupted traffic, power and water supplies as well as telecommunication in Yadong County, an area 40 km away from Sikkim.
Three people were killed at Lainchaur in Kathmandu, two in Sunsari district, and one each in Dhankuta and Sankhuwasabha districts in eastern Nepal, according to Home Ministry sources in the Nepalese capital.
Many buildings in and around Gangtok have collapsed and around 85 per cent of structures and houses have developed cracks due to the quake that hit Sikkim and other areas last evening, they said.
Most of the areas in north Sikkim have been cut-off from the rest of the country as roads were blocked and communication lines got snapped.
The Sadar police station in Gangtok was badly damaged due to the tremor. All BSNL telephone landlines in the city have gone dead since last evening.
The epicentre of the quake - the biggest in two decades - was located at Mangan and Sakyong areas, over 50 km from Gangtok on the Sikkim-Nepal border.
In Bihar, two persons were killed in Nalanda and Darbhanga districts, official sources said. A five-year-old girl and a youth were the two victims, they said.
Tremors were also felt in Assam, Meghalaya, Tripura, Jharkhand, Uttar Pradesh, Rajasthan, Chandigarh and Delhi.
Four teams of National Disaster Response Force have been rushed to Sikkim and five more teams were being sent from Kolkata, Cabinet Secretary Ajit Kumar Seth told reporters last night after a meeting of top officials in Delhi convened on the direction of Prime Minister Manmohan Singh.
"The Prime Minister himself is monitoring the developments connected to the quake," Seth had said.