A cracked wall of a house in Gangtok. (PTI)

Gangtok, Feb. 14: An earthquake measuring 5.7 on the Richter scale rocked Sikkim and north Bengal this morning, sending shockwaves through a region known to be a high-risk seismic zone.

Two army havildars, Rajinder Kumar and Virender Singh, were killed when their vehicle was hit by a boulder set loose by the tremors at the Sherathang international trade mart below Nathu-la.

The earthquake, which had its epicentre in Chungthang, 75 km north of Gangtok, lasted 22 seconds and caused extensive damage to property.

The Gangtok Raj Bhavan, Tashiling secretariat, Enchey monastery and the Sikkim Assembly building on Sonam Tshering Marg have reportedly developed cracks. State Bank of India’s branch at Zero Point had to be shut down for the day due to the large cracks that appeared in the ceilings and walls.

The old Raj Bhavan structure has been declared unfit. Governor V. Rama Rao was not present at his official residence. He was in his winter retreat in Rangpo. “Cracks have developed in the ceiling above the main staircase and there are fractured columns all around,” said N.T. Bhutia, the Raj Bhavan public relations officer.

Government staff refused to enter the Tashiling secretariat when they saw the extensive base-level damages. They, however, resumed their duties after being convinced by senior officials.

“A task force has been formed to assess the damage and take precautionary measures. A preliminary report will be placed tomorrow to decide which structures are unsafe. We have also decided not to allow any new building to be constructed above four storeys,” said chief secretary N.D. Chingapa.

North Bengal too felt the tremors but there were no reports of loss of life or property.