DHAKA, July 27: A series of tremors shook Chittagong and adjoining districts in a span of 15 hours on Sunday, leaving more than 50 people injured and some under-construction buildings and mud-wall houses collapsed.

The Geophysical Observatory Centre in Chittagong gave the number of quakes at four — in the early morning, at noon, in the evening and at night.

The strongest was at 5.09 on the Richter scale, the Observatory Centre recorded. The epicentre was located 186 kms off Chittagong.

According to reports from different localities, the tremors jolted the region of Chittagong Hill Tracts, specially Rangamati district, as well as the beach town of Cox’s Bazar and offshore islands.

The people of Rangamati were in panic as the series of earthquakes jolted the entire region till Sunday midnight, reports reaching Dhaka from Rangamati said.

Reports from Cox’s Bazar said that some 50 mud-wall houses were damaged. The 15-megawatt electric transformer at a sub-station in the city’s outskirts burst with a big bang, resulting in power outage in the nearby areas. A number of buildings, including the Divisional Public Library, developed cracks due to the tremor.

Chittagong city dwellers witnessed the first quake at about 5:20 am and that continued for 20 seconds. The second one with a minor intensity at 1:34pm was measured 3.69 on the Richter scale and it lasted for 13 seconds.

The third tremor at 6:08pm was measured at 4.79 on the Richter scale and lasted for 17 seconds, according to officials of the observatory. The fourth mild quake shook the port at around 8:30 pm.

DPA adds: The earthquake shook the Bangladeshi capital Dhaka for 20 seconds sending panic stricken residents into the streets, the state controlled Bangladesh radio said.