Nigeria's Boko Haram militants have attacked the north-eastern city of Maiduguri, killing at least 13 people.

They fired rocket-propelled grenades, but Nigerian troops were able to push back their advance.

The overnight attack came just hours after Muhammadu Buhari was sworn in as Nigeria's new president.

He has promised to take decisive action against the Islamic militants and has announced that Nigeria's military command centre will move to Maiduguri.

In recent years Boko Haram has killed thousands of people - mostly in north-eastern Nigeria - in its attempt to set up an Islamic state.

'Bright flashes'

Late on Friday Boko Haram fighters fired into the southern suburbs of Maiduguri around three hours.

"One of the blasts shook my roof so badly that I thought it must have landed on my house,'' resident Mari Madu told the Associated Press news agency.

President Buhari said Nigeria now had "a window of opportunity to fulfil her potential"

The Nigerian army deployed armoured vehicles and fired back, forcing the militants to retreat.

The BBC's Will Ross in Abuja says that the attack seems to be Boko Haram's way of showing that they remain a significant threat despite a recent military offensive against them.

In his first speech as president on Friday, Mr Buhari reiterated his commitment to tackle the group, which he described as a "godless group, who are as far away from Islam as one can think".

Mr Buhari, a former military ruler, has taken over from Goodluck Jonathan, who had been in office since 2010.

Nigeria's new president has also promised that the government will do everything it can to rescue more than 200 Chibok girls who were captured last year by Boko Haram.