An explosion that went off near a popular shopping mall in Nigeria's capital left no one hurt, but it heightened fears of attacks in a city that was once removed from unrest in Africa's most populous nation, authorities said Tuesday.

The nighttime blast did not damage any buildings, said National Emergency Management Agency spokesman Yushau Shuaib.

A police anti-bomb squad found another explosive near the blast site and safely detonated it.

The explosion comes just over a week after a bomb went off across the street from a popular nightclub in the city.

"The (police) are continuing their intensive overt and surveillance patrols of the city," said national police spokesman Frank Mba.

A radical sect known as Boko Haram has launched multiple attacks across Nigeria's north, but strikes on the capital are less common.

The group, whose name means "Western education is sacrilege" in the Hausa language, is waging an increasingly bloody fight with Nigeria's security agencies and public. More than 620 people have been killed in violence blamed on the sect this year, according to an Associated Press count.

The sect claimed responsibility for a suicide car bombing last August that hit the United Nations headquarters in the capital, killing 25 people and wounding more than 100 others.

A car loaded with explosives detonated in June 2011 at the federal police headquarters, killing at least two people. Analysts spoke of the growing sophistication of the Islamist insurgents with reported links to Al-Qaeda.

On New Year's Eve in 2010, a bomb exploded at a crowded and popular outdoor beer garden at a military barracks in Abuja, killing at least four people. No group claimed responsibility.