Updated at 9:50 a.m. ET
In the latest attack by the suspected Boko Haram extremists in Nigeria, militants shelled the northeastern city of Maiduguri, Reuters reports, quoting witnesses.
The BBC says fierce fighting is reported on the outskirts of Maiduguri, which is "home to tens of thousands of people who have fled Boko Haram attacks and was visited on Saturday by President Goodluck Jonathan."
"The assault on Maiduguri began just after midnight and that on Monguno later in the morning. At around 9 am (0800 GMT) on Sunday, a Reuters witness in Maiduguri said shelling could be heard and that military helicopters were circling the city.
"All roads have been closed, a security source said, and commercial activity has been shut down."
Later, Nigeria's military claimed to have repelled the attack, according to Reuters, which quoted security sources.
The reports come weeks after the Islamist extremist group killed as many as 2,000 people 100 miles northeast of Maiduguri, in the town of Baga. Both cities are in the border state of Borno, which has seen the brunt of attacks by the extremist group in recent months. Boko Haram also kidnapped hundreds of schoolgirls from the city of Chibok last April and the fate of most of them is still unclear.
The latest attack also comes as U.S. Secretary of State John Kerry is seeking to meet with Nigeria's president and his rival in next month's presidential elections in an effort to ensure the results of the poll will be accepted peacefully.