At least two people have been killed and 50 others injured in a series of small bomb blasts across Bangladesh.
The bombs were crude, homemade devices
Officials say more than 300 explosions took place simultaneously in 50 cities and towns across the country including the capital Dhaka.
An outlawed Islamic group, Jamatul Mujahideen Bangladesh, says it carried out the attacks.
Police say that more than 50 people have been arrested in connection with the blasts.
Prime Minister Khaleda Zia condemned the attacks as "cowardly".
"The attackers are enemies of the country, people, peace, humanity and democracy," she said.
Reports say many of the injured have been admitted to local hospitals, although most of the injuries are not life-threatening.
The blasts caused panic across many cities leading to massive traffic jams. Reports say parents rushed to bring their children home from school.
"It's an organised attack," said Home Minister Lutfozzaman Babor, adding that 58 of the country's 64 districts were affected.
In each incident, bombs were set off in crowded spots, mainly at government offices, journalists' clubs and courts, between 1030 and 1130 local time.
Mr Babor said timing devices were found at the scenes of blasts but most of the bombs were small, homemade devices - wrapped in tape or paper.
One of the deaths was a young boy in Savar, near Dhaka, who was killed when he picked up a device.
The other confirmed death was in the western town of Rajshahi, where doctors say a businessman died from wounds in an explosion.
Dhaka resident Jesin Zahir witnessed a blast near Jahangir Nagar university.
"It was a horrible experience. In the name of humanity, I ask all the extremist groups to please think twice before attempting this kind of coordinated crime."
Leaflets from the Jamatul Mujahideen Bangladesh have appeared at the site of some of the blasts.
"It is time to implement Islamic law in Bangladesh" and "Bush and Blair be warned and get out of Muslim countries", the leaflets say.
Early this year the Bangladesh government banned Jamatul Mujahideen and another group, Jagrata Muslim Janata Bangladesh
Security has been stepped up across the country
They were accused of being behind a series of bomb blasts, including those at two local aid agencies - Grameen and Brac.
The BBC's Roland Buerk in Dhaka said the banning was a major change in policy as the government had long insisted there was no threat from Islamic militancy.
Police and security forces were quickly deployed on Wednesday and were seen checking vehicles at Dhaka's main intersections.
Several unexplained bombs have exploded across Bangladesh in recent years.
On Saturday, one person was killed and 50 others injured after several bombs were thrown at a Muslim shrine in eastern Bangladesh.
In May last year, the British High Commissioner in Bangladesh was hurt in a grenade explosion at a Muslim shrine in the north-eastern town of Sylhet.
Three people were killed and more than 50 wounded in that attack.