About 20 people have so been found guilty in Nigeria for involvement with the Islamist militant Boko Haram group at closed-door trials taking place at a military facility in Kainji in north-central Niger state, a source has told the BBC.

They have been sentenced to between five and eight years in prison.

The trials started on Monday.

More than 1,600 Boko Haram suspects are to be tried in the coming weeks with a further 5,000 people after that.

Earlier today, Amnesty International said the secretive proceedings were denying the suspects the right to a fair court process.