Thirty were said to be in a serious condition

The authorities said the injuries occurred as prisoners rushed to get out of an old building, which they feared would collapse when the earthquake hit.

Thirty of those injured were said to be in a serious condition.

The meteorological office said the tremor was minor and lasted for nearly 20 seconds.

Officials said part of a staircase collapsed as prisoners fled the 150-year-old three-storey building.

No deaths reported

There were no reports of damage from other parts of the city, but police and paramilitary forces deployed around the jail to prevent any escape bids.

Police deployed to prevent a prison break

Home Minister Altaf Hossain Chowdhury told the AFP news agency that no deaths had been reported.

But reports said dozens of victims had been admitted to the Dhaka Medical College Hospital with fractured limbs.

Despite the relative weakness of the earthquake, which registered 3.82 on the Richter scale, many Dhaka residents ran out of their homes and offices during the tremor.

Bangladesh experiences about 25 mild tremors every years.

About 20 people died when an earthquake destroyed a building in the port city of Chittagong in 1997.