India, July 16 -- The political row over the detention of Bengali-speaking workers in various Bharatiya Janata Party-ruled (BJP) states over suspicions that they are illegal immigrants intensified on Wednesday with West Bengal chief minister Mamata Banerjee alleging that the drives were being conducted following a secret directive issued by the central to these governments.

"The Central government secretly issued a notification in February and sent it to BJP-ruled states asking them to arrest Bengali-speaking people. The notification says anyone can be kept in a detention camp for a month. Even people visiting their relatives are not being spared," Banerjee said, leading a protest march through Kolkata braving spells of rain.

"This is m...