A huge manhunt for Islamic militants is underway in Bangladesh, a day after what police say was the country's first suicide bombing.
Security has been tightened outside the High Court in Dhaka
The banned Jamaat-ul-Mujahideen group is accused of carrying out the suicide attack in Gazipur in which seven died.
A second, almost simultaneous, attack killed two policemen in Chittagong. The alleged bomber was seriously injured.
No group has claimed the blasts, which follow a wave of recent attacks. Police have detained a number of people.
Jamaat-ul-Mujahideen is one of three Islamic groups outlawed after the authorities linked them to a series of blasts earlier in the year.
Bangladesh Prime Minister Begum Khaleda Zia has promised tough action against the bombers, whom she called "enemies of Islam".
'Change in tactics'
Police say the Gazipur attack marks a major change in strategy by the militants.
They say the suicide bomber entered the lawyer's library in Gazipur's court compound wearing a lawyer's gown, underneath which explosives were strapped to his body.
Senior police officials say Jamaat-ul-Mujahideen has set up a 2,000-strong suicide squad to achieve its objective of establishing Islamic law in Muslim-majority Bangladesh.
A massive manhunt has been launched to identify and arrest potential suicide bombers, police say.
"Our target is to find out who these suicide squad members are, where are they are and how many there are," police intelligence chief Farrukh Ahmed told the AFP news agency.
It is not clear whether the attack in the southern port city of Chittagong was also meant to be a suicide bombing, or whether the bomber intended to escape.
Police say the attacker threw two bombs near the local courthouse, killing two policemen and seriously injuring himself.
A man police say carried out the attack is in hospital, and has had both his legs amputated.
Police have named him as Abul Bashar, from the northern district of Tangail. His father is among those detained for questioning.
Bangladesh has been hit by a wave of recent bombings that have targeted judges, journalists and politicians.
Police believe the courts and judges are targeted because they symbolise the country's laws, most of which are secular and based on British legal code.
Leaflets purportedly left by the militant group at some blast sites have called for the establishment of Sharia law in Bangladesh.