Cities and towns across Bangladesh have been hit by scores of small explosions. Leaflets from a banned Islamic group were found near some of the blasts that killed one person and injured at least 44.
Police say the bombs exploded almost simultaneously near bus and train stations, courts and government buildings, and airports and markets in several cities including the capital Dhaka and the port city of Chittagong.
The junior minister for Home Affairs, M. Lutfuzzaman Babr, called it "an organized attack."
Leaflets found at some of the explosion sites carried a call by a banned Islamic group called Jamaat-ul-Mujahideen for Islamic rule in Bangladesh.
Ataus Samad, a writer and independent political analyst in Dhaka, says the bombings caused fear throughout the country.
"People are scared," he said. "The government is also quite puzzled, and I would say they are quite scared because they have to find out who has done it."
Bangladesh has the world's third largest Muslim population. The Jamaat-ul-Mujahideen was banned in February along with another Islamic group after an earlier series of bombings against non-governmental groups, holy shrines and other targets.