Report claims Nigerian authorities ignored school warnings

A British team has arrived in Nigeria to help with the search for more than 200 schoolgirls kidnapped by Islamist extremists a month ago.

It comes amid claims from Amnesty International that the Nigerian military had received a warning that there would be a raid and failed to act.

It is a charge the country's information minister said he doubts - however, he said the authorities would still investigate the claims.

The BBC's World Affairs Editor John Simpson reports from Nigeria's capital Abuja.