DC Khondoker Atiar Rahman told reporters that on Tuesday afternoon he received a letter from a person named Ripon, who claimed himself as a JMB commander. The letter was posted at a Dinajpur post office on May 6, he said.

The DC said he informed the law enforcement agencies of the matter.

The letter reads, "We will blow up some important establishments including your office within one and two days as you killed our leaders."

Superintendent of Police Hasif Aziz said adequate security measures were taken at different government offices including the DC office. Dinajpur police were also trying to find out the sender.