LAGOS, Nigeria -- A member of a radical Muslim sect with "al-Qaida links" helped mastermind the bombing of the UN headquarters in Nigeria's capital, the nation's secret police said yesterday, a worrying sign that international terror groups may be seeking a foothold in the oil-rich country.

The State Security Service issued a statement to journalists saying six days before the attack it arrested two other men suspected of planning it.

The bomb tore through the Abuja headquarters of the world body, killing 23 people and wounding 81.

The attack raised new questions about Nigeria's ability to fight terrorism as the radical Boko Haram sect stages increasingly bloody sectarian attacks against the nation's weak central government.

The secret police said it received information Aug. 18 that an attack in the capital would come from Boko Haram, which campaigns for the implementation of strict Shariah law.

On Aug. 21, officers arrested Babagana Ismail Kwaljima and Babagan Mali, two men the agency said had ties to Boko Haram and were planning the attack. The agency said a third suspect, Mamman Nur, remained at large.

"Investigation has revealed that one Mamman Nur, a notorious Boko Haram element with al-Qaida links who returned recently from Somalia, [worked] in concert with the two suspects [in] masterminding the attack on the United Nations building in Abuja," the agency said.

The agency statement, the first confirmation from Nigeria's government of Boko Haram's involvement, also implicates transnational terrorism in the bombing after warnings from others that the sect had reached out to other terror groups.

Earlier this month, the commander for U.S. military operations in Africa told The Associated Press that Boko Haram may be trying to coordinate attacks with al-Shabab in Somalia and al-Qaida in the Islamic Maghreb, which operates in northwest Africa.

Nigeria, a nation of 150 million people, is split largely between a Christian south and a Muslim north.

Latest videos