COX'S BAZAR, BANGLADESH (AFP) - A Muslim activist accused of campaigning in refugee camps for the unconditional return of displaced Rohingya to Myanmar has been arrested in Bangladesh, police said.

More than 600,000 Rohingya have fled to Bangladesh since Aug 25, when coordinated attacks by the Rohingya insurgency prompted a massive crackdown on the Muslim minority by the Myanmar military.

Only accredited charities are allowed to operate in the sensitive border region and Bangladesh has heavily curtailed access to the vast camps.

Mahbubul Alam Minar was detained more than a week ago, but police only confirmed late on Sunday that he was being held on suspicion of erecting banners listing Rohingya demands in English and Bengali.

An investigation has been opened into Minar, who has links to Jamaat-e-Islami, the largest Islamist political party in Bangladesh, deputy police chief in the Cox's Bazar border district Afrozul Haq Tutul told AFP.

Bangladesh authorities are wary of Islamist groups - most notably the armed Arakan Rohingya Salvation Army fighting for the stateless minority - gaining a foothold in the vast refugee camps.

Police believe Minar acted alone in hanging the banners, which claim to represent the previously-unknown Committee on Rohingya Rights Establishment, and broadcasting his efforts on social media.

The banners called for all displaced Rohingya to be granted safe passage back to Myanmar, compensation for their destroyed homes and return of seized land.

They also demanded Myanmar's western-most Rakhine State adopt the Rohingya name Arakan, and that Muslims there are granted full religious freedom, rights to education and a separate judiciary.

Bangladesh wants the Rohingya repatriated and has offered to stage a joint military push with Myanmar against the militants active in the border regions.

It has reinforced police checkpoints, deployed plain clothes officers and bolstered security in the camps to intercept any militants trying to mingle with civilians crossing the border.

"There is no way they can enter here," Cox's Bazar police chief Iqbal Hossain told AFP.