Twelve people were killed and 20 injured following a suicide bomb attack in the north-eastern Nigerian town of Potiskum.

There was no immediate claim of responsibility for the blast but it bore the signs of similar attacks by Nigeria's home-grown Boko Haram Islamic extremist group.

In a separate attack in Kano, two male suicide bombers left a vehicle at the Kano Line bus station, before detonating themselves.

In Potiskum, bus driver Adamu Isa said the man forced himself onto the bus and blew himself up.

In the same town on Sunday a girl who looked about 10 carried explosives that detonated, killing herself and four others at a market.

Thousands of people have been killed in the five-year-old uprising to enforce strict Islamic law in Nigeria.

Boko Haram now controls vast swathes of north-east Nigeria and has displaced more than three million people.

The mounting threat of the Islamist insurgency has already led to the postponement of February's presidential elections, with the vote now due to take place on 28 March.

The delay is designed to give the Nigerian military time to re-establish its presence in the north-east.

However, opponents of President Goodluck Jonathan have claimed that the delay is actually a political tactic.