"Sleeper Cells," the notorious killer gangs blamed for hacking and butchering people allegedly for hurting Islamic sentiments, are still active in the capital and across the country.
Police and intelligence agencies say there are about 100 Sleeper Cells operating all over the country, proving attempts by law enforcers to tame them either ineffective or futile.
The cells, each made up of 3 to 7 members, have been carrying out assassination of anti-Islamists across the country, an intelligence source told the daily Observer on Tuesday. Most of the cells appear to have been "brainwashed" by Islamic radicals and extremists trying to enforce Sharia law in Bangladesh, thwarting democracy and secularism that have been enshrined in the country's Constitution.
They kill people without knowing whether they are doing right or wrong, the sources said.  
They have been 'blinded" by ego and sort of wild zest that provoke "mindless" killings and ruthless attacks on who they consider as atheists or non-believers of the Muslim faith.
Why they have been given the incriminating title "Sleeper Cells" is mysterious but many people including some members of the law enforcing agencies think the cells have been named so because they operate "silently" without alerting or waking up the victims or the law men.
The Sleeper Cells are one of the most dreaded killer gangs in Bangladesh, and seem to have been supported by extremists from outside the country, too. They deploy "brainwashed" locals to complete the operation.  
The cell members have no educational background or understanding of the religion - making them just tools in the hands of the "master" who propagate "death" to people possessing free and progressive thinking.
One sources said that intelligence agencies have identified the "sleeper cells" after the killing of online activist Washiqur Rahman Babu on 30 March in 2015.  
Zikrullah and Ariful Islam, two suspects who were caught by a mob and handed over police soon after the killing of Washiqur, belong to one such cell, the source added.
Investigators suspect that "sleeper cells" members were involved in the killing of Faisal Arefin Dipan of Jagriti Prokashoni at Aziz Supermarket in Shahbagh and injuring Shuddhoswar's Ahmedur Rashid Tutul and two bloggers Ranadipam Basu and Tareque Rahim in the capital's Lalmatia in separate attacks on Saturday.
Investigators suspect that "sleeper cells" were also behind the killing of Bangladesh-born US citizen and blogger Avijit Roy Avijit, Niladri Chattopadhyay Niloy, Ananta Bijoy Das 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 militancy expert of the Rapid Action Battalion (RAB). "They have developed skills and the technology to hoodwink the police. But it's not too hard a nut to crack," the RAB official added.
A sleeper cell consists of secret agents who receive specialised training in their home countries (Bangladesh or elsewhere) and are then "assigned" to assimilate themselves into the targeted people. Only 3 to 4 cells members take part in each killing mission.  
Mysteriously, one sleeper cell member does not know comrades belonging to another cell and also have no communication outside their own cell. The cell members use local weapons while carrying out their killing missions, law enforcing agencies said.
With the killing of Washiqur Rahman, the religious fanatics killed 16 people between 2004 and 2015. The other victims include 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. Most of the "sleeper cells" operate keeping law enforcers in "sleep" and run away without being caught or even noticed.
These sleeper agents may spend years as students, traders or just "anyone", till they suddenly receive orders from their overseas handlers to either commit an act of terrorism or provide aid to those carrying out such acts. Individual members of a sleeper cell may not even be aware of each other - so that they cannot reveal identity of 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 militant outfits Jamaat-ul-Mujahideen Bangladesh (JMB), 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 cell members to communicate with their comrades and disseminate directives to kill selected targets. The entire process is carried out evading the eyes of law enforcement agencies.