A Bangladesh court on Sunday sentenced three Rohingya extremists of a now defunct militant group to 10 years in jail for possessing bomb-making materials, a prosecutor said.

The trio were arrested in 2014 in Dhaka with materials to be used for making improvised explosive devices (IEDs), said Salahuddin Howlader, a prosecutor at the Metropolitan Special Tribunal in the capital.

They were found guilty and sentenced immediately under the country's explosives laws, the prosecutor said, adding one of them was sentenced in absentia as he was on the run.

“They were involved with several international militant outfits including the RSO,” he told AFP, referring to the Rohingya Solidarity Organisation, a small militant group that was active in Myanmar's northern Rakhine state in the 1980s and 1990s.

Local media, citing the police charge-sheet on the case, said the three men were suspects in the 2014 Burdwan blast in the neighbouring Indian state of West Bengal that killed at least two people and wounded several while they were allegedly making IEDs.

“The charge-sheet read the accused admitted planning sabotage in Bangladesh with the assistance of international Islamist extremist outfits,” the online edition of the mass circulation Bengali daily Prothom Alo said.

In recent years, the Arakan Rohingya Salvation Army (Arsa) has emerged as the main Rohingya militant group operating in Myanmar's troubled Rakhine state that borders Bangladesh's southeast.

In August 2017, Arsa attacked several police posts in Rakhine prompting a massive military crackdown that forced some 740,000 Rohingya Muslims to flee to Bangladesh, where they are housed in squalid refugee camps. The refugees joined some 300,000 Rohingya who have been living in the camps for years and even decades.

Bangladeshi security officials say no extremist groups such as Arsa or RSO operate in the camps, but this week the International Crisis Group said militants were increasing their grip on the settlements and were responsible for the murder of at least one Rohingya camp leader.

The conflict research group has urged Bangladesh to step up its police presence in the camps, saying gangs and extremist groups were now operating openly in the settlements.

Threats from extremists had left Rohingya leaders fearful for their lives and frequent murders were rarely investigated, the group said.

Bangladesh police said the creation of seven new police posts, the deployment of armed officers and better intelligence had improved security.