Police and intelligence sources said, three government officials, two top district level politicians, one from the opposition party and two journalists, who helped law enforcers detect and arrest JMB cadres after the August 17 bomb blasts, are on the hit list.

The authorities asked them to move cautiously, sources said.

Meanwhile, security measures have been beefed up in the district, they said.

Confirming existence of JMB suicide squad here, the members of law enforcement agencies said, the killing squad entered the town, in groups, on Wednesday and took shelter somewhere to accomplish their task.

Earlier, Satkhira police arrested JMB cadre Nasir Uddin with the help of an eye-witness. He blasted bombs on the court premises on August 17. After his confessional statement, police arrested seven JMB cadres with the help of an official of intelligence agency, a local journalist and a pick pocket, also an eye-witness.

Now, JMB has sent a suicide squad targeting them and some others, sources said.

Earlier, Islamist militants sent letters to government officials, lawyers, teachers and journalists including Deputy Commissioner (DC), Superintendent of Police (SP), Upazila Nirbahi Officer (UNO) and Assistant Commissioner (AC-Land), threatening to kill them and blow up their offices and residences.

When contacted, Satkhira SP Abdur Rahim told The Daily Star adequate security measures have been taken at all key installations in the town.