Abuja - The United States wants to help Nigeria fight Islamists it sees as a growing regional menace, but the country cannot rely on military might alone, an official travelling with U.S. Secretary of State Hillary Clinton said.
Clinton visited Africa's most populous nation on Thursday and met with President Goodluck Jonathan. Washington is offering support in the fight against Boko Haram, a Taliban-like group that wants to create a strict Islamic state in Nigeria's north.
She said Nigeria was "one of the most vitally important strategic partnerships in sub-Saharan Africa" in remarks at the U.S. embassy, shortly before leaving.
Africa's top oil producer is a major exporter of light crude to the United States, whose refiners favour it because it is easy to refine into motor fuel. Its proven oil and gas reserves outweigh those of the rest of sub-Saharan Africa put together.
Boko Haram has launched bomb and gun attacks on churches this year that provoked Christians, leading to deadly reprisals against Muslims. Hundreds of people have died and Washington is concerned about insecurity spreading.
"Northern Nigeria also borders Chad, it borders Cameroon, it borders Niger and we are concerned this radicalism could undermine the security of neighbouring states," the senior U.S. official said.
Jonathan's critics say he relies too much on the military to defeat Boko Haram, rather than addressing northerners' grievances, such as poverty and unemployment.
"A security strategy is not enough," the official said.
Military crackdowns have mixed results - hurting Boko Haram in some areas but angering people by their heavy handedness.
Washington will offer Nigeria help with forensics, tracking of suspects and "fusing" disparate strands of police and military intelligence, the U.S. official said.
"We know all too well from our own experiences in both Iraq and Afghanistan what can happen if soldiers and police are not operating under appropriate authorities."
"We will encourage them not to use excessive force and to look at this as a ... law enforcement operation," he added.
On Thursday, the Nigerian military swept through Kogi state in search of gunmen behind a massacre on Monday in which the attackers blocked exits to the Deeper Life Church in the town of Okene and fired at trapped worshippers, killing 19.
Gunmen killed three people in an attack on a mosque in the city the next day. Boko Haram have been known to attack churches and mosques.
"We have so far arrested four people including a woman. We trailed them to their hideout," Kogi state police commissioner Mohamed Katsina told Reuters by phone.
Residents complained of heavy-handed tactics in the security forces' raid, underscoring the U.S. official's concern.
"The army are raiding our houses one after the other, beating and brutalising people," said Rahamman Bello, a resident of Adavi village on the outskirts of Okene.
"Many of our people are being arrested and molested."
Clinton was also due to address a law on oil production that has been stuck in parliament for more than five years, leaving majors such as Exxon and Chevron uncertain about the regulatory future in Nigeria.
The official said Clinton would urge a "fair and predictable environment" for oil companies in the Petroleum Industry Bill.
"If a bill comes out which appears to undermine the interest of companies, they won't invest," the official said.