DHAKA, Bangladesh - As thousands of Shiite Muslims gathered for a religious procession before dawn Saturday, unidentified attackers hurled home-made bombs that exploded in the crowd and killed a teenage boy while injuring more than 100 others in Bangladesh's capital, police said.

Police said the attack on Shiites - a minority in the Sunni-dominated country - was unprecedented for Bangladesh, which has seen a rise in violence this year claimed by extremist Islamist groups amid political instability.

Authorities immediately arrested two suspects and recovered two unexploded bombs, but they dismissed the attack as an attempt to further destabilize the country. No group immediately claimed responsibility.

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"Given the nature of attacks, I think this has been done to create chaos in the country. It is sabotage," Dhaka's senior police official Asaduzzamn Mia said. "But it is clear that it was a planned attack."

Witnesses said some 25,000 had started gathering at 2 a.m. for the 8-kilometer (5-mile) march through Dhaka's older quarter from Huseni Dalan, an important 17th century Shiite center of learning, to a mosque.

Of the five bombs thrown into the crowd, three exploded, sending thousands of panicked people fleeing in all directions.

Relatives cried out for their loved ones in the dark. Shoes and sandals littered the pavement, along with colorful flags and chains used by youths to beat themselves during the procession to show their grief for Ashoura, a 10-day religious ritual marking the death of Imam Hussein, the grandson of the Prophet Muhammad.

One 15-year-old boy died from shrapnel wounds just before reaching the hospital and was taken to the mortuary, where his brother sat wailing outside the front door.

Most of the injured were in stable condition at local hospitals or had been released within a few hours, said Dr. Nazimun Nesa of the state-run Dhaka Medical College Hospital.

Dhaka medicine shop owner Mohammed Sajib was at the procession with family and friends.

"Suddenly, the bombs exploded near me, and we started running," he said. "My hands are covered in blood. We took many to the hospitals."

Bangladesh has been rocked by a series of attacks claimed by Islamist extremists this year, including the murder of four atheist bloggers and, more recently, the killing of two foreigners - an Italian aid worker and a Japanese agricultural worker.

The Islamic State extremist Sunni militant group claimed responsibility for killing the foreigners, though the government immediately dismissed the claims and said there was no evidence of the group having a presence in Bangladesh.

Shiites are a minority in the country but they are generally not discriminated against, and attacks against them are virtually unheard of.

"This is unprecedented. We have been observing this for ages but we never faced anything like this," Feroz Hossain, curator of the Huseni Dalan building, told reporters.

After the attacks, the participants said they were determined to carry on with the ritual.

"We are not afraid," Rashed Hossain said on the street near the Huseni Dalan, where thousands of others were still gathered at noon. "We are ready to move ahead with the procession."

Meanwhile, police experts were examining the blast scene, collecting evidence and planning to study closed-circuit TV camera footage from in and around the shrine, said Col. Ziaul Ahsan of the special anti-crime agency Rapid Action Battalion.

Prime Minister Sheikh Hasina, a moderate who pledged to stamp out militant radical groups, has overseen the arrest of dozens of suspected militants and the banning of six groups in recent years. Experts say the crackdown has left some of the country's more hardline Muslims feeling alienated, and has led to a resurgence in Islamist group activity.

The violence has rattled foreigners and threatened the impoverished country's economy, which relies heavily on foreign aid and a $25 billion garment industry producing clothing and fashion wear for top international brands.

In another attack in Pakistan against Shiites processing for Ashoura, a suicide bomber blew himself up and killed 18 others in the southern Pakistan city of Jacobabad on Friday, police said. Shiites are regularly targeted in attacks in Pakistan.