AFP/Dhaka

At least one person was killed and nearly 80 wounded Saturday in a bomb attack on the main Shia shrine in the Bangladeshi capital as thousands gathered for the annual Ashura procession, police said.

Police said they believed it was the first time Bangladesh's Shia Muslim community had been targeted, though the bombing comes just weeks after an Italian aid worker and a Japanese farmer were shot dead in attacks claimed by the Islamic State group.

Officers said a 14-year-old boy died on the spot after three small bombs were thrown at the complex of the Hossaini Dalan, the main Shia site in the old Mughal quarter of Dhaka, at about 2:00 am Saturday (2000 GMT Friday).

‘There were some 20,000 people in and outside the building at that time. They were preparing to hold the annual Muharram mourning procession when the three (bombs) were exploded,’ deputy commissioner of Dhaka Police Mofiz Uddin Ahmed told AFP.

The attacks come as Shias around the world mark the holy month of Moharram. Pakistan's Shias have also suffered sectarian violence this week after two suicide blasts killed at least 27 people.

In Bangladesh, television showed live footage of the chaos in the aftermath of the blasts with fleeing people, many holding flags, and ambulances taking the injured to hospital.

Local police chief Azizul Haq said at least one person was killed and around 80 injured in the attack, which took place on the premises of the 17th century religious site.

‘We've recovered two unexploded bombs. These are like explosive devices and almost like grenades and fitted with batteries,’ Haq told AFP, adding that one person had been detained.

Police inspector Mozammel Hoque told AFP that most of the injured were hit by bomb splinters. At least one person is in critical condition.

‘Some 50 were brought to the Dhaka Medical College Hospital. A 14-year-old boy was brought in dead. He died due to the explosion,’ he said.

No one has yet claimed responsibility for the attack.

- Blast hit Ashura mourners -

Authorities have yet to make any arrests in connection with the blasts but three people have been taken in for questioning, police inspector Mohammad Murad told AFP.

Home Affairs minister Asaduzzaman Khan Kamal told local media that authorities had video footage of the blasts and he hoped they could quickly track down the attackers.

Witnesses told the mass-circulation daily Prothom Alo that many mourners fell to the ground as loud explosions went off at the main gate of the Hossaini Dalan, the most important prayer and congregation site for Bangladesh's Shias.

Roni, who uses one name, said mourners dressed in black were holding prayers just before the procession when he heard 8-10 explosions and saw a fire.

Security was stepped up at Shia mosques across the country immediately after the attack and mourners in Dhaka's Mohammadpur neighbourhood banned women and children from the procession.

Defying the attack, about 20,000 Shias continued the procession in Dhaka, police and an AFP photographer at the scene said, cutting their bodies with knives and iron chains in a religious ritual.

‘We've been observing this mourning procession here for centuries. But we've never seen any incident like this. We demand a quick and fair investigation into the blasts,’ a leader of the Shia community at Hossaini Dalan told reporters.

While the blasts are believed to be the first attack on Shias in Bangladesh, in the past two years banned militant groups have killed more than a dozen Sufi Muslims and attacked Hindus and Christians.

The killing of four atheist bloggers this year has also undermined government efforts to play down the threat posed by hardliners, experts say.