Cameroonian troops crossed the border into Nigeria, killed about 150 villagers, burnt their huts and forced them to flee, Nigerian refugees said Tuesday after walking for days to reach a refugee center.

Cameroon's government denied the charges, that came amid growing tensions between Nigeria and its neighbors over the Boko Haram Islamic uprising that has spilled over Nigeria's borders.

Farmer Mariamu Abubakar said Cameroonian soldiers on November 30 killed about 150 people in his village near Nigeria's Banki border post, stole their livestock and set their huts ablaze.

He was among 643 refugees who arrived Monday night at Adamawa's Fufore transit center. Soldiers who screened them said they came from Gamboru to Banki, a 150-kilometer (95-mile) stretch along Nigeria's border with Cameroon.

While it is unclear who attacked whom and why, it is "a real humanitarian disaster," said David Miliband, the visiting president of the New York-based International Rescue Committee. "They are unable to go home because it's not yet safe and because they fear for their lives."

Nigeria's Petroleum Minister said last week he expects a major oil discovery soon in the Lake Chad Basin, likely to fuel more border conflicts in the northeastern part of Nigeria that joins Chad, Cameroon, and Niger.

Earlier Tuesday, Gov. Bindow Jibrilla of Nigeria's northeastern Adamawa State accused Nigeria's neighbors of sending their nationals into his state disguised as refugees. Jibrilla told reporters he didn't know why it was happening but that there were thousands.

Cameroon said its troops fighting "in synergy" with Nigerian soldiers carried out a "coordinated operation" on several border villages around Lake Chad November 27 to November 29. He said they freed at least 900 people held by Boko Haram extremists.

"We have a highly trained military that respect human rights," said Cameroon government spokesman Issa Tchiroma Bakary. He denied Cameroon has forcefully evicted Nigerian refugees though Nigerian officials have reported receiving several thousand in recent months.