Dhaka: A bomb exploded Friday at a mosque of the minority Ahmadi Muslim group in Bangladesh's northwestern town of Bagmara leaving the suspected suicide bomber dead and three other people injured, police said.

Police said the bomb blast occurred when the small Ahmadiya Muslim Jamaat mosque at Bagmara, some 250 kilometres (150 miles) from the capital, Dhaka, was packed with worshippers during Friday prayers.

"One person died on the spot and three other people were injured. It seems he was carrying the bomb and it looks like it was a suspected suicide blast," local police chief Motiar Rahman told AFP.

Ahmad Tabshir Choudhury, a spokesman of the Ahmadiya Muslim Jamaat in Bangladesh said there were two unknown people who came to the mosque where nearly 100 people including women joined the Friday prayers.

"The bomb was detonated during the prayers. One of the two unknown people died. It appears that he was a suicide bomber," Choudhury told AFP.

He added that four Ahmadi Muslims were injured including one whose condition is serious.

No group has claimed responsibility, but in recent months, homegrown outlawed militant group, Jamayetul Mujahideen Bangladesh (JMB), and Islamic State group claimed responsibility for bomb attacks on a top Shiite shrine and a Shiite mosque in northern Bangladesh.

Members of other minority groups, including Sufis -- who adhere to a mystical form of Islam deemed by some Islamist hardliners as heretical --  have also been attacked and killed, and two Christian priests have survived attacks claimed by Islamist militants. 

Bangladesh has been roiled by rising unrest which has seen four atheist bloggers and a publisher hacked to death this year.

Two foreigners have also been shot dead -- a Japanese farmer and an Italian aid worker -- while several priests were threatened and two policemen hacked to death

Last week two bombs exploded at a mosque inside a navy base in Bangladesh's port city of Chittagong , injuring at least six people. Local media put the toll much higher.

Police blame the JMB for the recent violence while Prime Minister Sheikh Hasina's government accuses the main opposition party and its Islamist ally of trying to trigger anarchy. 

The parties deny the claims.  

Analysts say Islamist militants pose a growing danger in conservative Bangladesh and that a long-running political crisis has radicalised opponents of the government.

Ahmadis are a tiny Muslim group in Bangladesh. In the past, its members have been attacked by hardline Islamists and often barred from setting up mosques.