Police in Bangladesh have arrested four members of the jihadist group Jumatul Mujahideen Bangladesh (JMB) suspected of hacking an English professor to death.

The Islamic State (ISIS/ISIL) claimed responsibility for killing professor Rezaul Karim Siddique, 58, on April 23 while he was on his way to work at the state-run Rajshahi University located in the city of the same name, accusing of him of atheism.

However, Bangladeshi authorities have rejected the claim, denying that ISIS maintains a presence in Bangladesh despite a wave of attacks in the country for which ISIS has claimed responsibility.

Among the four suspects arrested in connection to the professor’s killing was JMB regional commander Maskawath Hasan Sakib, nicknamed Abdullah, “who confessed involvement in the attack before a magistrate, leading to the arrests of the three other suspects on Monday night, according to Rajshahi Metropolitan Police Commissioner Mohammed Shamsuddin,” reports the Associated Press (AP).

In a November 2015 article published in its propaganda magazine Dabiq, ISIS refers to JMB as a “proper jihad organization,” prompting speculation that the two groups are linked.

However, in the past, JMB has been associated with the Kashmir-based Lashkar-e-Tayyiba (LT), a jihadist group linked to ISIS rival al-Qaeda.

“Of the arrested four, three directly took part in the killing while the fourth man was waiting with a motorbike they used,” reportedly said police chief Shamsuddin.

The police chief refused to identify the three other suspects “for the sake of the investigation” but added that the motorbike had been confiscated.

Shamsuddin is quoted by AP as saying, “Abdullah told police during his interrogation that the attackers did not know why Siddique was targeted, and that they had carried out the killing on orders from their superiors.”

JMB, founded in 1998, was thought to have been in hiding since six of its leaders were hanged in 2007.

The jihadist group is “committed to establishing an Islamic state in Bangladesh through violence,” according to a November 2011 article published by the Combating Terrorism Center at West Point, NY, in its journal, the CTC Sentinel.

According to the article:

[JMB] stormed onto South Asia’s jihadist scene with a synchronized, country-wide bomb assault on August 17, 2005. The group detonated approximately 460 bombs within a 30-minute period at 300 locations in 63 of the 64 districts in Bangladesh.

Later in 2005, JMB targeted the country’s judiciary—court buildings, judges, and government officials—with suicide attacks in an effort to intimidate authorities into releasing around 400 JMB suspects arrested after the August countrywide blasts.

Bangladesh, a Muslim-majority nation of 160 million people, has experienced a spate of attacks over the past year in which atheist bloggers, academics, religious minorities, and foreign aid workers have been fatally targeted, notes Reuters.