In a remote district of northeast India, 30ft-high walls and watchtowers are rising from the open countryside as workmen pour concrete over a vast expanse and stab girders into the mud.

Hidden from the eyes of the world, these men are building a colossal detention centre, the first of ten planned for the impoverished, tea-growing state of Assam. Thousands of people could be sent here, with little hope of leaving, in one of the biggest exercises in forced statelessness ever attempted.

The project has been shrouded in secrecy, but The Times has visited the site of the new detention centre, in Goalpara district, which will have capacity for 3,000 inmates when completed, and could expand further.

Activists stage a protest in Calcutta against the implementation of the National Register of Citizens GETTY IMAGES

Assam has applied to build nine more such