Police announced a two million taka ($25,000) reward for information leading to the arrest of Canadian citizen Tamim Chowdhury, who disappeared after allegedly masterminding the cafe attack.
Chowdhury is accused of heading a faction of the Jamayetul Mujahideen Bangladesh (JMB) homegroup militant group, blamed for scores of murders of members of religious minorities.
Police are also searching for sacked army major Syed Mohammad Ziaul Haq and offering a similar reward. He is accused of heading a second group, Ansar al Islam, suspected of killing a series of secular bloggers and activists.
“We are trying to arrest them. We believe if they are brought to justice….we can eliminate extremism from the country,” national police chief A.K.M. Shahidul Hoque told reporters.
Authorities are under great pressure to crack down on extremism in Muslim-majority Bangladesh after a recent increase in gruesome attacks.
Five gunmen stormed an upscale cafe in the capital on July 1. They killed 20 mainly foreign hostages and two police officers in Bangladesh’s deadliest single militant attack of recent years.
The Islamic State group has claimed responsibility for the cafe siege, releasing images of the carnage and a photo of the attackers posing with its black flag.
Hoque reiterated that police have no evidence of IS involvement, saying “these are homegrown extremists. They are mainly JMB members” although they sympathised with the jihadist group.
Hoque said 30-year-old Tamim, who was born in Bangladesh, planned the attack on the cafe after returning from living in Canada in 2013.
Releasing details of the second wanted Islamist, Hoque said Haq was sacked from the army in 2011 for his role in a failed military coup.
Authorities say the two homegrown extremist groups have been responsible for killing at least 80 people over the last three years, including foreigners.
Hoque defended police progress in tracking down those behind the mayhem, saying officers “have arrested 172 people for their involvement in the incidents”.