DHAKA: Police in Bangladesh have arrested eight suspected militants, including the chief of the outlawed Jamaat-ul Mujahideen, as authorities step up a crackdown on hardline Islamists.

Bangladesh, a Muslim-majority nation of 160 million people, targeted the militants after machete-wielding attackers this year hacked to death three online critics of religious extremism, including American blogger Avijit Roy.

Police also seized explosives and other bomb-making materials during overnight raids on the militants' hideouts in the capital, Monir-ul-Islam, joint commissioner of the detective branch of Dhaka police, said on Tuesday.

"During the raids we arrested six militants, including the head of Islamist outfit Jamaat-ul-Mujahideen," he said. They were plotting to "kill important personalities of the state and free their leaders from jail," Islam added.

Indian security officials uncovered a plot against Bangladesh Prime Minister Sheikh Hasina in October, after two members of the group were killed in an explosion while building bombs in the state of West Bengal, which borders Bangladesh.

The banned Jamaat-ul-Mujahideen was thought to have been lying low after facing action by authorities following its detonation of nearly 500 bombs across the country almost simultaneously on a single day in 2005.

Its militants later carried out attacks on several courthouses, killing 25 people and injuring hundreds.

Bangladesh security forces this month arrested 12 suspected militants, including the chief of Al Qaeda in the Indian Subcontinent, which claimed responsibility for a string of attacks in Bangladesh and Pakistan, including that on Roy.

In May, Bangladesh also arrested three suspected members of Islamic State, including an IT manager at a subsidiary of Coca-Cola Co in Dhaka, amid growing fears that the militant group could be extending its influence in South Asia.

Police said they were checking if any of the eight people arrested this week had ties to Islamic State.

“We are also checking if they have any connection with Islamic State,” Islam said.

Read more: Another blogger hacked to death in Bangladesh