Mamunur Rashid
As many as 100 sleeper cells are operating across the country, including the capital Dhaka, an intelligence source told The Daily Observer on Sunday.
The cells, made up of between 3 to 7 people, were reportedly carrying out assassinations of anti Islamists across the country. 
The source said that intelligence agencies have identified the "sleeper cells" after the killing of online activist Washiqur Rahman Babu. Zikrullah and Ariful Islam, who were caught by a mob and handed over to the police soon after the killing of online activist Babu, belong to one such cell, the source added.
Investigators suspect that separate "sleeper cells" were behind the killing
of Avijit and Washiqur. But they have
no idea who recruited and trained these members.
"Yes, sleeper cells are present in the capital, no doubt about that," said a senior militant expert of the Rapid Action Battalion (RAB). "They have developed skills and the technology to hoodwink the police, but it's not such a hard nut to crack," the RAB official added.
A sleeper cell consists of secret agents who receive specialised training in their home countries or states and are then "assigned" to assimilate themselves into the targeted people.
Mysteriously one sleeper cell members do not know the members of another cell and also have no communication outside their own cell. The cell members use local weapons while carrying out their killing missions. 
With the killing of Washiqur Rahman, the religious fanatics killed 16 people between 2004 and 2015. The other victims are a Bangladesh-born US citizen bloggers Avijit Roy, Ahmed Rajib Haider, Ashraful Alam, Arif Raihan Dwip, three Rajshahi University (RU) teachers, Prof AKM Shafiul Islam Lelin, Prof Yunus, Prof Sheikh Taher Ahmed, Dhaka University (DU) teacher Prof Humayun Azad, Ahle Sunnat Wal Jamaat leader Nurul Islam Farooqi, self-declared 'Pir' Lutfar Rahman Faruk, his eldest son and four other followers. Intelligences sources said the members of sleeper cells were behind most of the killings.
These sleeper agents may spend years as faceless people, including as students or traders, till they suddenly receive orders from their overseas handlers to either commit an act of terrorism or provide aid to those carrying out the act. Individual members of a sleeper cell may not even be aware of each other - a vital way of protecting the identity of the others during police interrogations.
Lt Col Mohammad Abul Kalam Azad Director (intelligence) at RAB headquarters said, "The number of sleeper cells may have increased in recent years."  Banned Jamaat-ul-Mujahideen Bangladesh (JMB), banned Islamist militant outfit Hizb-ut-Tahrir (HuT) and Ansarullah Bangla Team (ABT) have several teams of sleeper cells, he added.  Each cell operates under a terrorist group or organisation.
Middle East-based militant organization ISIS has sleeper cells around the world. Another militant organization al-Qaeda also has several sleeper cells.
Hidden IP addresses are now being used by JMB, HuT and ABT sleeper cells members to communicate with its members and disseminate directives to kill selected targets, the entire process is being carried out evading the eyes of law enforcement agencies.
These hidden IP addresses are also used by the leaders of the banned militant outfit JMB to communicate with its "sleeper cell" members, who remain dormant in strategic positions until receiving an order to attack.