At least 54 people have been killed in three explosions in the north-eastern Nigerian city of Maiduguri, police say.

A spokesman blamed the Islamist militant group Boko Haram for the attack on Sunday night. The group was founded in Maiduguri.

The police told Reuters news agency that a further 90 people were injured in the blasts.

The BBC's Will Ross says it is now clear that this was one of the most deadly attacks in recent months.

One bomb exploded at a mosque, while the other two detonated at an area where people gather to watch football, said emergency services spokesman Muhammad Kanar.

The blasts in Maiduguri reflected the "high level of desperation" in Boko Haram, spokesman Sani Usman said in a statement.

The group wants to establish Islamic rule in the north-east. Two million people have been forced from their homes since the militants launched their insurgency in 2009.

Nigerian President Muhammadu Buhari made combating the group a key campaign pledge as he sought election this year.

Boko Haram at a glance:

- Founded in 2002, initially focused on opposing Western-style education - Boko Haram means "Western education is forbidden" in the Hausa language

- Launched military operations in 2009

- Thousands killed, mostly in north-eastern Nigeria, abducted hundreds, including at least 200 schoolgirls

- Joined Islamic State, now calls itself "West African province"

- Seized large area in north-east, where it declared caliphate

- Regional force has retaken most territory this year