Muhammadu Buhari has been sworn in for a second term as president of Nigeria at a ceremony in the capital, Abuja.

The president took his oath of office in traditional dress - simple white robes and an embroidered hat.

"I do solemnly swear that I will be faithful and bear true allegiance to the Federal Republic of Nigeria," he said.

"I will preserve, protect and defend the constitution," he added.

Mr Buhari's to-do list includes reviving a weak economy and tackling rampant corruption and insecurity.