Nigeria's main presidential challenger has said he will not hold talks with Islamist militants if he wins elections next month.

In an interview with the BBC, Muhammadu Buhari said Boko Haram was not interested in peace.

"If they are interested in peace, how can they kill 13,000 Nigerians?" he asked.

The 72-year-old former military ruler also said it was not a good idea to postpone the elections, which were due to be held earlier in February.