An earthquake of 4.3 magnitude on the richter scale shook parts of Meghalaya on Monday, the seismic observatory Shillong said.

The mild intensity quake was recorded at 12.52 AM and its epicentre was located along the Meghalaya-Bangladesh border, officials at the observatory said.

There have been no reports of any damage or injury.

A 6.8 magnitude tremor, epicentered on the Sikkim-Nepal border, was felt across north and east India last evening. It was followed by two aftershocks measuring 6.1 and 5.3 on the Richter scale.

Last evening's tremor was the biggest quake felt in the Northeast since 1988.

Quake toll rises to 40, relief operations in full swing

The death toll in the powerful earthquake rose to 40 with 19 people being killed in Sikkim, five in West Bengal, seven each in Nepal and Tibet even as rescue and relief operations were on Monday stepped up in the affected areas.

Over a hundred people have been injured in the 6.8 magnitude tremblor 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, officials 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 on Sunday 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.

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Over 5,000 troops, 9 choppers sent to quake-hit areas

Over 5,000 troops and nine helicopters have been dispatched by the army to carry out rescue and relief operations in quake-hit Sikkim, officials said on Monday.

"Around 5,000 troops in 105 columns and four ALH Dhruv and five Cheetah helicopters have been deployed in the relief operations by the army in the state," army officials said in New Delhi.

The troops include elements from both the infantry and engineers, who are involved in deploying heavy equipment and clearing road blocks at several places in the state, they said.

Officials said that two jawans were killed in north Sikkim in the quake while the three missing vehicles last night have been located and all the troops in them are safe.

They said that army formations in the state have been engaged in providing food and shelter to people in affected areas. At least 2,000 people have been provided help by the army, they said.

The earthquake, which measured 6.8 on the richter scale, has also caused substantial damage to certain military buildings in the area.

The IAF, on its part, has already deployed five aircraft -- two C-130Js, two AN-32s and one Avro -- for relief operations.

Landslides, rain affect rescue operations in Bengal

Rescue operations in the quake-hit areas of north Bengal were affected on Sunday after heavy rains and landslides in several parts of Darjeeling hills snapped road communication even as the death toll rose to five in the state.

"Reports reaching Kolkata said two deaths were reported from Kalimpong and one each from Siliguri and Jalpaiguri and one in the tea garden of Doors," state chief secretary Samar Ghosh told PTI.

State commerce and industry minister Partha Chatterjee, on way to Siliguri, said that he would hold a high-level meeting there to step up rescue operations and arrange rehabilitation of the affected people in Darjeeling hills.

North Bengal development minister Goutam Deb was asked by chief minister Mamata Banerjee to coordinate with Chatterjee during his visit to the quake-hit areas.

Harka Bahadur Chetri, GJM MLA from Kalimpong, said power supply was restored in the area this morning but the tremor has left a trail of devastation in the entire hills.

Several buildings were damaged and developed wide cracks, he said, adding that landslides occurred in many areas of Kalimpong and the road link to Siliguri and Sikkim was blocked.

The chief minister has been personally monitoring the situation and two control rooms were set up for giving information - one for Kolkata and another for north Bengal.

Meanwhile, the entire administration has been asked to be on the alert and be ready for any eventuality, sources said.

Rescue teams, doctors yet to reach quake affected areas

Around 400 personnel of National Disaster Response Force (NDRF) and a team of 20 doctors, sent to Sikkim for rescue and relief operations, have not been able to yet reach the quake-hit areas due to blockade of roads following landslides, officials said on Monday.

Five teams of NDRF consisting of 203 personnel along with necessary rescue equipment, who have been dispatched from Delhi, reached Bagdogra in West Bengal this morning, they said.

"They are still held up at the transit camp in Bagdogra due to landslides which have blocked roads at various places along the highway," a Home Ministry spokesperson said.

Another five teams of NDRF consisting of 200 personnel have left Kolkata. Of them, 100 personnel have arrived at Bagdogra while another 100 personnel were expected to land there shortly.

Officials said over 700 personnel of Indo-Tibetan Border Police were already engaged in rescue and relief operations in Sikkim.

A medical team comprising four surgeons, seven orthopaedics, five anaesthetists, two neuro-surgeons and two other specialists which has been sent for Sikkim from Delhi reached Bagdogra this morning.

They too have not been able to reach the affected areas and are held up at Bagdogra due to landslide causing road blockage, officials said.

As per official information received by the Home Ministry, 14 people have lost their lives and 94 others have been injured in the quake. Sikkim has officially reported seven deaths and 64 injured, Bihar has reported two deaths, West Bengal five deaths and 29 injured while one person has been injured in Assam.

"The state governments are ascertaining the extent of damage," the spokesperson said.

Sikkim, West Bengal, Bihar, Assam, Arunachal Pradesh, Meghalaya, Manipur and Mizoram have been affected by the 6.8 magnitude tremblor.

The Border Roads Organisation (BRO) has conveyed that there have been 16 landslides on a stretch of 10 km in Sikkim and efforts were on to clear the roads.

"The situation is being closely monitored and every possible assistance is being extended to the state governments," the spokesman said.