Dhaka, Bangladesh - Several small bombs exploded at three railway stations in emergency-ruled Bangladesh on Tuesday with evidence pointing to Islamic extremists blamed for persecuting a Muslim sect, officials said.
The homemade bombs went off at stations in the capital, Dhaka, the northern city of Sylhet and southeastern port of Chittagong, causing panic but leaving just one person with minor injuries, police said.
Railway officials said leaflets and an inscribed metal plate, likely to be linked to the bombings, were found at two of the stations.
The metal plate, signed by "Zadid (new) Al-Qaeda," made death threats against minority Ahmadiyas -- an Islamic offshoot sect frequently targeted by extremists from the majority Sunni Muslim community of about 100,000.
It also threatened charity workers.
It declared contact with Ahmadiyas and workers of non-governmental organisations (NGOs) was "prohibited," adding that "Ahmadiyas should accept Mohammad as the last and the greatest prophet."
Ahmadiyas break sharply with mainstream Islam by not believing that Mohammad was the last prophet. Extremists in Bangladesh have previously called on the government to pass a law declaring them "non-Muslim."
National police chief Nur Mohammad said all the blast sites had been cordoned off and intelligence officers had begun an investigation.
"We are investigating whether it is a new group," he said.
Officers would also examine if an existing group had adopted new tactics, he added.
"Nobody has claimed responsibility for the blasts but we are working on the theory that the group named on the metal plate, Zadid Al-Qaeda, is responsible," said railway police officer Abdur Rahman, adding no arrests had been made so far.
In August 2005, more than 400 explosive devices were detonated almost simultaneously in towns and cities across Bangladesh, marking the start of a nationwide bombing campaign by a group calling for the imposition of strict Islamic law.
Six people blamed for masterminding the campaign were hanged in March after being convicted of the the murder of two judges.
They included the leader of the group, Jamayetul Mujahideen Bangladesh (JMB), Shaikh Abdur Rahman and his deputy, Siddiqul Islam.
The bombing campaign rocked moderate Bangladesh and forced the then government to admit it had underestimated the threat from Islamic extremists.
In June 2005, the New York-based Human Rights Watch criticised the country's former coalition government, led by the Bangladesh Nationalist Party (BNP), for complicity in persecution of the Ahmadiyas.
It accused two of the government's coalition partners -- Jamaat-e-Islami and Islami Oikya Jote -- of inciting violence against the minority.
A report by the organisation documented a "campaign of violence, harassment and intimidation" by the Khatme Nabuwat (KN) -- an umbrella group of Sunni Muslim extremists.