A bomb attack on a busy shopping district in Nigeria's capital, Abuja, has killed at least 21 people and injured 52 more.

The blast, near the popular Banex plaza shopping complex in Wuse district, could be heard from miles away and sent plumes of smoke into the air.

Police say a suspect has been arrested. No group has claimed responsibility.

Islamist militant group Boko Haram has bombed targets in Abuja and across northern Nigeria recently.

'Covered in blood'

Chiamaka Oham, who was near the site of the blast, told the BBC: "We heard a really loud noise and the building shook, and people started screaming and running out.

"We saw the smoke and people covered in blood. It was just chaos."

The area was packed with shoppers at the time of the blast, the BBC's Hausa service editor Mansur Liman reports.

Many cars outside the shopping complex were burnt out and many windows were shattered, he adds.

One man told the BBC his driver was killed in the blast: "I was in the complex when I saw that the ground was shaking. I saw my driver dead and a lot of casualties."

Government spokesman Mike Omeri confirmed that the blast was the result of a bomb attack.

Boko Haram has staged previous attacks in Abuja, but most of its targets have been in the north-east of the country.

In April, more than 70 people were killed in a bomb blast at a bus stop on the outskirts of the capital in an attack claimed by Boko Haram.

The group also said it was behind a car bomb attack near a bus station in the suburbs in May, which killed at least 19 people and injured 60 others.

The group also carried out a deadly car bomb attack on the United Nations building in the Nigerian capital in 2011.

It has become a source of growing international concern since the recent abduction of more than 200 girls from a school in northern Nigeria.