Associated Press

LAGOS, Nigeria (AP) _ Security forces raided areas near the site of two bombings in Nigeria’s capital and detained eight suspects including foreigners on Saturday, the Ministry of Defense announced as the city prepared to host a three-day international conference.

All schools and government offices in Abuja, the capital in central Nigeria, will close during the May 7-9 World Economic Forum on Africa, according to a presidential order that follows two bomb attacks in three weeks that killed nearly 100 people. Islamic extremists are blamed for both.

A statement Friday night said the measure “is to ease the flow of traffic” during the conference, to which hundreds of international personalities, business and African leaders are invited. Chinese Premier Li Keqiang is the guest of honor.

One more victim died in the hospital, raising the toll to 20 dead from Thursday’s bombing, the permanent secretary of health, Dr. Demola Onakomaiya, said Saturday. He appealed to relatives to claim the corpses, saying hospital morgues are overloaded and still hold many victims from the April 14 blast that killed at least 75 people. A final toll, to include pathologists’ estimates of the number blown apart by the powerful explosion, has never been given.

The government said it is deploying 6,000 police and troops to help secure the event, and President Goodluck Jonathan has assured delegates they will be safe.

Further indicating Nigeria’s security threats, the U.S. Embassy warned Americans in an email Friday that “groups associated with terrorism” may be planning “an unspecified attack” on a Sheraton hotel in Nigeria’s commercial capital, Lagos.

The hotel chain has two locally owned franchises in the southwestern city of about 20 million people. A duty manager at the $350-a-night Sheraton in Ikeja suburb, near the international airport, said he was unaware of any threat. He spoke on condition of anonymity because he is not authorized to speak to reporters.

Maj. Gen. Chris Olukolade, the Defense Ministry spokesman said in a statement Saturday that the eight people detained Saturday “are helping ongoing investigation with useful information.” He said most of them are foreigners, without identifying nationalities.

In a separate operation in the northeast, he said a Chadian named Usman Mecheka who was “operating with the terrorists around Lake Chad” has been detained. Olukolade said the Chaidan had been trying to extract a ransom from herdsmen and farmers after an earlier attack.

Extremists killed four villagers in a pre-dawn attack Saturday on the outskirts of Maiduguri, capital of the northeastern state of Borno, the spokesman said. Security forces used mortar shells to repel the militants and kept them out of the city, he said.

Explosions on April 14 and May 1 in Abuja, in the center of the country, are blamed on the Islamic extremists Boko Haram terrorist network which has recruited fighters in neighboring Chad, Niger and Cameroon amid fears that its 5-year-old uprising could spread in the region. More than 1,500 people have been killed in the insurgency this year, compared to an estimated 3,600 between 2010 and 2013.

Militants of Boko Haram _ the nickname means “Western education is sinful” _ are holding some 276 teenage girls abducted from a northeastern school April 15. The extremists have targeted schools and slaughtered hundreds of students.

In response to national outrage and protests at the failure to rescue the girls, Jonathan on Friday announced a that presidential committee headed by a retired general will mobilize people in the area of the mass abduction and other citizens “for a rescue strategy and operation” and to “articulate a framework for a multi-stakeholder action for the rescue of the missing girls.”

Unverified reports this week that the militants are demanding ransoms for their release coincided with stories that some of the girls and young women _ they are aged 15 to 18 _ have been forced to “marry” their extremist abductors and some have been carried across borders into Chad and Cameroon.

The attacks and the prolonged captivity of the girls have gravely undermined confidence in Jonathan and his government as Nigeria prepares for February 2015 elections.

Nigeria is fighting a 5-year-old Islamic uprising by extremists whose stronghold is in the remote northeast but who are threatening attacks across Africa’s biggest oil producer.