A Boko Haram attack in the Nigerian city of Maiduguri killed at least 15 people and wounded 83, a military spokesman said on Monday, in the biggest strike since the government said it was in talks with the Islamist militant group.

The military said the incident occurred late on Sunday and included gun battles between government troops and the militants as they tried to enter Maiduguri, a city in northeast Nigeria which is the epicentre of a nine-year conflict with Boko Harm that has caused the deaths of more than 20,000 people.

President Muhammadu Buhari has prioritised improving security and has previously declared the defeat of Boko Haram, which is trying to establish an Islamic state and which split into two factions in 2016.

The military said troops clashed with the jihadists in a cashew plantation around Bille Shuwa and Alikaranti villages, near Giwa barracks on the edge of Maiduguri's inner city, at around 08:10 pm (1910 GMT) on Sunday and fought gun battles with government troops during which multiple blasts were heard.

'Fifteen persons including a soldier have so far been confirmed dead in the encounter, while about 83 persons who suffered varying degrees of injuries are receiving due medical attention,' said army spokesman Colonel Onyema Nwachukwu.

He said 13 insurgents had been killed, including seven bombers, adding that the retreating militants attacked locals.

'It is clear that the remnants of the Boko Haram terrorists are hell-bent on remaining relevant by attacking soft and vulnerable targets,' Nwachukwu added.

It is the most significant attack on the city since the government said last week it was in talks with the insurgents with the aim of securing a permanent ceasefire.

The government has not disclosed which elements of Boko Haram it is in discussions with and it was also not clear which faction carried out Sunday's attack.

The government has been saying since December 2015 that the jihadist group has been defeated but high-profile attacks in the last few months - including the kidnap of 111 schoolgirls from the town of Dapchi and a strike in the town of Rann that killed three aid workers - has shown the jihadists remain active.

All but one of the girls taken from Dapchi, in Yobe state, on February 19 were returned by the militants in March. The government later said it had negotiated their release as part of broader talks.

In early 2015 Boko Haram controlled a swathe of land in northeast Nigeria around the size of Belgium but was forced out of most of that territory by the army with the support of troops from neighbouring countries.

Since then the group has continued to carry out suicide bombings, gun raids and kidnappings in northeastern Nigeria as well as in neighbouring Cameroon, Niger and Chad.