There have been simultaneous bomb attacks at three railway stations in Bangladesh, officials say.
The bombs were kept in cotton bags
The blasts caused panic among commuters and the railway terminals were evacuated. One man was injured.
The explosions went off at stations in capital Dhaka, the northern city of Sylhet and the south-eastern port town of Chittagong.
Messages left at two of the sites in Bengali and English said the attacks were carried out by "the new al-Qaeda".
'Prepare for death'
"We are investigating whether it is a new group," national police chief Nur Mohammad said, the AFP news agency reports.
The bombs were in cotton bags. The one casualty, at Chittagong station, was a rickshaw driver who was hit as he tried to open the bag, police said.
Police say the messages were left on thin metal plates. They contained warnings against non-governmental organisations (NGOs) and also against Bangladesh's minority Muslim Ahmadiyya sect.
Correspondents say that hardline Islamic groups in Muslim-majority Bangladesh oppose the activities of NGOs, which are often funded by Western donors and employ women.
"Stop associating with non-believers. Stop working for NGOs by 10 May or prepare for death," said the etched messages signed by Jadid (New) al-Qaeda Bangladesh, a hitherto unknown group.
The bombs went off at the start of a two-day public holiday and caused chaos and panic in all three railway stations - which were more crowded than usual as people travelled to see friends and relatives.
The BBC's John Sudworth in Dhaka says that the authorities are investigating whether Jadid al-Qaeda is a new group, or a manifestation of a hardline group that already exists.
Security has been tightened since the blasts
The bombs themselves have been described as crude devices. The remains of charred packaging wrapped in black tape - with a pencil battery and a small clock attached - were found at the site of the Dhaka blast.
In recent years, Bangladesh has seen violence by militants wanting to establish strict Islamic practices in the country.
In August 2005, more than 300 explosive devices were set off almost simultaneously in 50 cities and towns across Bangladesh.
An outlawed Islamic group, Jamatul Mujahideen Bangladesh (JMB), said it carried out those attacks.
While the JMB has attacked NGOs and the Ahmadiyyas in the past, there is so far no concrete evidence linking it to Tuesday's blasts.
Ahmadiyyas do not believe that Mohammad was the last prophet and the JMB has demanded in the past that the government declare them as "non-Muslims".