Nigeria's ambassador to the United States has berated Washington for refusing to sell "lethal weapons" to fight his country's Islamic uprising, saying the extremists otherwise would have been defeated long ago.

Adebowale Ibidapo Adefuye said the United States is letting down an old ally in its hour of need, and Nigeria's people and government feel abandoned.

"The U.S. government has up till today refused to grant Nigeria's request to purchase lethal equipment that would have brought down the terrorists within a short time," Adefuye told members of the Washington-based Council on Foreign Relations Monday night.

"We find it difficult to understand how and why, in spite of the U.S. presence in Nigeria with their sophisticated military technology, Boko Haram should be expanding and becoming more deadly."

Adefuye said that Washington has refused Nigeria's requests to buy heavy weaponry because of allegations the defense forces have violated the human rights of Boko Haram suspects. It was not possible to get an immediate response from U.S. officials but U.S. laws ban sales of lethal weapons to countries whose military are accused of gross human rights abuses.

Adefuye dismissed the allegations as rumors spread by political opponents as Nigeria prepares for presidential elections in February.

An Associated Press investigation found Nigerian troops responsible for the deaths of thousands of detainees since a state of emergency was imposed in May 2013 in three northeastern states.

In the latest such report, community leaders and family members told AP that soldiers raided poor homes in Potiskum, capital of Yobe state, on Nov. 5 and dragged away young men aged from 18 to 30. Soldiers later dumped 18 bullet-ridden bodies at the hospital mortuary, according to hospital records that identified victims including a tailor, a butcher, a student and a cattle trader.

The military has not responded to requests for comment on that incident.

The killings came two days after a suicide bomber killed 30 people in a procession of moderate Muslims.

On Monday, Potiskum was further terrorized when a suicide bomber killed 48 students at an all-boys high school.

The continued violence comes despite the Nigerian military's claim on Oct. 17 that Boko Haram had agreed to an immediate cease-fire. The militants have denied there is any truce and have responded with more and deadlier attacks. The extremists now control a swath of territory in northeastern Nigeria estimated to cover 7,700 square miles along the border with Cameroon. The Nigerian military -- badly paid, demoralized and riddled with corruption -- has not been able to stop the Islamic militants from seizing more towns and cities.

President Goodluck Jonathan Wednesday declared his government will defeat Boko Haram.

"We must defeat terror," he said before a crowd at an Abuja stadium, announcing that he will run for re-election in February. "We are equipping the armed forces and deploying special forces this time to engage the terrorists and end this senseless war."

He also promised, again, to "get our daughters free," referring to the more than 200 schoolgirls kidnapped in April whose plight has attracted international outrage.

Boko Haram is better equipped than the military, mainly with arms looted from barracks and abandoned by fleeing troops, say governors in the northeastern states, other politicians and soldiers who have deserted the front.

Nigeria has made at least two failed attempts to buy helicopter gunships and other weapons in South Africa. In September, South African customs officials seized $9.3 million in cash flown in on a private jet by two Nigerians and an Israeli. It was a "legitimate arms deal," said PRNigeria, a public relations firm that promotes the Nigerian government.

In October, South Africa froze $5.7 million wired to the account of a South African arms dealer by Nigeria, saying the dealer no longer had a license to export weapons. Nigeria's Senate Defense Committee is investigating.

Local press in Nigeria have quoted security officials saying the country recently took delivery of some attack helicopters from China, but those reports have not been verified.