A bomb is believed to have exploded in the outskirts of the town of Maiduguri, in northern Nigeria.
Maiduguri is the capital of Borno state, the epicentre of terror group Boko Haram's deadly insurgence.
It is not yet clear whether the explosion caused any casualties. The incident occurred days after the government announced commercial flights would resume in Maiduguri, months after the local airport was closed over security concerns.
Who are Nigeria's Boko Haram terrorists?
Boko Haram (recently renamed Iswap) fights against Western influence in Nigeria and aims to impose its version of Sharia law in the country.
The group declared an Islamic caliphate in Gwoza, along the Cameroon border, in August 2014.
Boko Haram has raided several cities in the north of the country in a bid to take control of more land.
Three states − Adamawa, Borno and Yobe − have been under a state of emergency since May 2013, due to Boko Haram's attacks.
The group has killed more than 2,900 people since the beginning of 2015.
Earlier in July, a suspected Boko Haram twin bomb attack on a mosque and a restaurant in the provincial Nigerian capital of Jos killed at least 44 people and injured 67.
A few days later, another bomb went off at Port Harcourt, the capital of the oil-rich River State. No casualties were reported.
Boko Haram, which aims to establish an Islamic caliphate in northern Nigeria, often carries out bomb attacks throughout the north of the country, where thousands have been killed in recent years.
In June, Nigeria's President Muhammadu Buhari announced the military headquarters would be relocated from Abuja to Maiduguri until the fight against terrorism was over.
The Nigerian government is currently aided by mercenaries and troops from neighbouring countries Chad, Benin, Niger and Cameroon in its offensive and has scored some successes since the military cooperation started in February.
The US announced it would send military trainers to help the Nigerian army improve its intelligence gathering and logistic.