Dhaka: A man blew himself up on Friday at a camp for Bangladesh's elite security forces, wounding two others, in an apparent botched suicide attack.

The incident came a day after a series of raids on suspected militant hideouts in the troubled country, which has suffered a series of Islamist attacks in recent years.

Home Minister Asaduzzaman Khan said a man carrying explosives entered the Rapid Action Battalion (RAB) camp near the Dhaka international airport on Friday morning.

The explosives went off after he was challenged by two RAB men, wounding them both but causing no other casualties. 

"Security has been beefed up at all international and domestic airports," Bangladesh Civil Aviation authorities' spokesman Rezaul Karim told reporters.

The bomb exploded after the man, who entered the camp by jumping over a wall, was confronted by RAB officers, RAB spokesman Mufti Mahmud Khan told reporters. It was not clear whether the detonation was deliberate.

The spokesman said the man's identity was not known, but that the attack was similar in style to that of previous ones by Islamist extremists.

The attacker was in his late 20s, local newspaper Daily Star said, quoting witnesses.

"The force of the blast was such that it ripped apart his torso and sent pieces of him flying in all directions for about 15-20 metres," the newspaper said.

After the attack, a bomb disposal unit swept the spot and recovered a live improvised explosive device (IED), RAB spokesman said.

The camp, which hosts a mix of elite police, army and air force personnel, has since been cordoned off.

Bangladeshi security forces launched a nationwide crackdown on Islamist extremists following a deadly siege at a cafe in Dhaka last year, arresting scores.

The drive was led by the RAB, which is tasked with tackling militancy and serious crimes in Bangladesh.

Four alleged militants were killed on Thursday when a raid on a building in the southern port city of Chittagong sparked a 15-hour stand-off with militants armed with guns and grenades. 

Police said they were all members of the extremist group Jamayetul Mujahideen Bangladesh (JMB) and that at least two were killed by a suicide explosion that they set off.

Last year's attack on the Holey Bakery, a cafe popular with foreigners, badly undermined Bangladesh's reputation as a relatively moderate Muslim nation.

The Islamic State group claimed responsibility for the attack, in which 22 people including 18 foreign hostages were killed in July.

The Sheikh Hasina government has denied the presence of IS in the country and blames local extremists. 

Rohan Gunaratna, a professor of security studies at Nanyang Technological University in Singapore, warned that the Bangladesh government needed to acknowledge the threat to tackle it comprehensively. 

"Denying IS will neither help to secure Bangladesh nor create the mindset required to counter the rising threat," he told AFP.