Appeasement kills.

ABUJA, Nigeria (AP) — Nigeria detained and released several radical Muslims suspected of being terrorists in 2007 — including a man who officials now say helped organize last week’s deadly car bombing at the United Nations headquarters in the nation’s capital, a high-ranking official told The Associated Press.

The men arrested four years ago had allegedly been caught with explosives. Their rapid release from detention was apparently aimed at placating Muslim groups, but it has now come back to haunt security officials who fear a growing wave of al-Qaida-linked terror attacks in Nigeria, a main supplier of oil to the United States.

Some of those arrested in October 2007 were even plotting to carry out attacks in the United States and to attack American targets here, in Africa’s most populous country, said the official, who claimed direct knowledge of the arrests. He spoke on condition of anonymity due to the political sensitivity of the case and because he is not authorized to discuss the matter with journalists.

Nigeria remains very sensitive to any suggestion it is a haven for terrorists, and the information released at the time of the arrests was fairly vague. It was not immediately clear if Nigeria shared information about the purported anti-U.S. plots with U.S. officials. The U.S. embassy had no immediate comment Thursday.