Nigerian police say one of two suicide bombers that struck at a northeastern town on Tuesday was a child.

The girl, who appeared to be between 12 and 14 years old, blew herself up at the crowded entrance to the main bus station in Damaturu, killing six other people and wounding 41 others.

Minutes later, a young male bomber killed only himself when his device exploded prematurely.

Witnesses described seeing a "young girl" approach the station at 7 a.m. local time (0600 UTC) and refuse to undergo a security search at the gate.

She detonated the explosives on her body as a car pulled out of the bus station, killing six people inside the vehicle.

A spokesman for the Yobe state police said the injured were receiving treatment in hospital.

No one immediately claimed responsibility for the two attacks, but they were immediately blamed on Boko Haram, the Islamist militant group that has captured large parts of northern Nigeria.

They happened a few hours after United Nations Secretary-General left Nigeria following a two day visit.

Boko Haram have increased attacks in northern states of Nigeria since President Muhammadu Buhari took office in May, promising to tackle the deadly insurgency.

Two weeks ago, 150 people were killed by drowning or shooting during a raid on the village of Kukuwa-Gari.

Last month, a suicide bomber detonated explosives inside his car at a security checkpoint in the city.

Previously, the jihadists have used dozens of girls and women in suicide bombings and often dress men up in women's burqas to carry out attacks.

As well as Nigeria, the group has targeted neighboring Chad, Cameroon and Niger.

Over the past three months, more than a 1,000 people have died.

mm/jil (AFP, AP)