A twin bomb attack has taken place in a busy area of the Nigerian city of Jos, killing at least 30 people, witnesses say.

The two bombs exploded in quick succession, close to the scene of a major bombing in May.

The city of Jos has a mixed population of Muslims and Christians, and in recent years suspected Boko Haram militants have attacked churches there.

The Islamist militant group frequently carries out suicide attacks in Nigeria.

There has been no claim of responsibility for Thursday's explosions in Jos.

The blasts targeted the city's commercial district, near the Terminus bus station.

Witnesses told the Associated Press news agency that the first explosion took place at an outdoor food stand. The second blast hit a marketplace.

Separately, police in Nigeria's second-largest city, Kano, say they have arrested a 13-year-old girl wearing a suicide belt.

On Wednesday, at least four people were reported killed and seven hurt in attacks by two female suicide bombers in Kano.

And last month, more than 100 people died in a gun and bomb attack during prayers at one of the biggest mosques in the city.

Boko Haram militants are suspected of being behind the attacks.

Some 2,000 people have died in violence blamed on the Islamist militants this year.

The group has taken over several towns and villages in the north-east of the country, declaring the area under its control to be a caliphate.

Thousands of people have died and more than a million have been forced from their homes in the group's five-year insurgency.