Reports from northern Nigeria say that the attorney-general of Kaduna state is dropping charges against the jailed Islamist leader, Sheikh Zak Zaky, and three of his followers.

A statement from the attorney general's office said the authorities had decided it was no longer necessary to continue proceedings.

It gave no further details.

Sheikh Zak Zaky was arrested two years ago, and charged with inciting disaffection.

A correspondent for the BBC in Kaduna says Sheikh Zak Zaky is likely to remain in detention until his trial formally resumes in January.

In September, supporters of Sheikh Zak Zaky appealed to the Nigerian military ruler, General Abubakar, to release him.