YOLA, Nigeria (Reuters) - Nigerian community leaders demanded on Friday that the air force be prosecuted for alleged attacks on their villages in the northeasterly state of Adamawa, which they say killed 78 people.

The human rights campaign group Amnesty International has said at least 35 people were killed in air raids in the region on Dec. 4. The Nigerian Air Force rejects the allegation, saying that it opened fire to dissuade looters and vandals, but did not target people.

The allegations highlight some of Nigeria’s security challenges, which have become politically charged less than a year before an election. President Muhammadu Buhari is touring affected areas, including the state where 110 schoolgirls were abducted last month, though he will not visit Adamawa.

Residents of the Adamawa villages described being fired upon by a fighter jet and military helicopter as they attempted to flee while, at the same time, hundreds of herdsmen were staging a revenge attack on the communities for earlier killings over grazing rights.

“We call for national and international criminal investigation in order to commence prosecution of those responsible for this crime,” the representatives of six of the villages said in a joint statement.

They said more than 78 people had been killed by Nigerian Air Force jets, and 20 by herdsmen.

“We want the Nigerian Human Rights Commission and international community to know that the Nigerian Air Force excessively used force unlawfully in its air raids on our villages,” read the statement, presented at a news conference in Adamawa’s state capital, Yola.

Following Amnesty’s report, the air force denied it had bombed any locations in the region or fired at people. It said it was unaware of any human casualties.

“Our position remains as captured in our earlier response to Amnesty International,” air force spokesman Olatokunbo Adesanya said on Friday.

U.S. Secretary of State Rex Tillerson is due in Nigeria next week for a visit expected to focus on security.

Nigeria is in the final stages of buying fighter planes from the United States. The deal was halted by the previous U.S. administration over concerns about the military’s human rights record, but revived by the administration of President Donald Trump.