However, the militia group added that it would welcome any talks with tribal leaders instead.

For this purpose, these exits were to be defended by an armed militia group and by hunters.

But another assessment has concluded that the drop might simply be down to militia groups becoming more creative in covering up their crimes.

Neither has proved capable of reining in the militia groups fighting for the two presidential rivals.

Militia groups clashing over the area's natural resources and a deep suspicion of outsiders wearing hazmat suits have presented emergency teams with a complex and dangerous challenge.