MAIDUGURI, Nigeria, Jan 10 (Reuters) - A bomb worn by a girl aged about 10 exploded in a busy market place in the northeastern city of Maiduguri on Saturday, killing at least 16 people and injuring more than 20, security sources said.
"The explosive devices were wrapped around her body and the girl looked no more than 10 years old," a police source said.
Maiduguri, the capital of Borno state, lies in the heartland of an insurgency by Sunni Muslim militant group Boko Haram, and is often hit by bomb attacks.
A Nigerian security source said the bomb went off at 12:15 p.m. (1115 GMT). The bodies of at least 16 bomb victims were counted in one hospital by mid-afternoon, civilian joint task force member Zakariya Mohammed told Reuters.
"Right now, there are 27 injured people in Borno Medical Hospital, while more were taken to other hospitals," he said.
The northeast states of Borno, Yobe and Adamawa are bearing the brunt of a five-year-old insurgency by the Boko Haram, which wants to revive a medieval caliphate in Nigeria -- Africa's most populous country and its biggest energy producer.
Last year more than 10,000 people died in the bloodshed.
About 130 km (80 miles) away in the Yobe state capital Damaturu, the army managed to repel an Islamist militant attack on Friday evening, but not before considerable damage was wreaked in the area, a Reuters reporter in the city and witnesses said.
The Reuters witness saw a number of burnt buildings, including the police area command station and a mosque in the Abacha market, along with several shops.
No casualty figures were immediately available and the militants took their dead away with them. Damaturu was last attacked in early December when air strikes were needed to halt advancing militants.
On Saturday afternoon, two suicide bombers, arrested by police in a vehicle, blew themselves up when they were taken to the main police station in the town of Potiskum in Yobe state, residents who witnessed the scene said.
There was no immediate word on casualties.
The Boko Haram revolt is seen as the gravest security threat facing Nigeria, a country of 170 million people, and a headache for President Goodluck Jonathan, who is seeking re-election in a national ballot set for Feb. 14. (Reporting By Isaac Abrak in Kaduna, Lanre Ola in Maiduguri and Joe Hemba in Damaturu; Writing by Julia Payne; Editing by Mark Heinrich and Crispian Balmer)