U.S. forces killed an estimated 20 Islamic State militants in a hotly contested corner of Nigeria, days after an operation that killed the group’s No. 2 , U.S. and Nigerian officials said Monday.

The U.S. airstrikes, near the northeastern village of Metele, were the result of close intelligence sharing between the Nigerian and American militaries, according to officials.

“Terrorists who threaten our citizens, communities and national stability will be located and defeated,” Maj. Gen. Samaila Uba, a Nigerian military spokesman, said. “There will be no safe haven for terrorists anywhere in Nigeria.”

Relations between the U.S. and Nigeria, a powerhouse in West Africa, frayed last year when President Trump accused the Abuja government of failing to protect Christians from Islamist militants.

Since then, Nigeria has allowed hundreds of American troops to be posted to the country to train Nigerian forces and coordinate targeting of militant groups that have rampaged through the Lake Chad Basin for years. The U.S. has greater air capabilities than Nigeria, and has conducted the actual strikes.

“The removal of these terrorists diminishes the group’s capacity to plan attacks that threaten the safety and security of the U.S. and our partners,” U.S. Africa Command said Monday.

U.S. officials said no American or Nigerian troops were injured in the latest operation, which took place on Sunday.

On Friday, Trump announced that a joint operation in Nigeria had killed Islamic State’s alleged second in command, Nigeria-born Abu Bakr ibn Muhammad ibn ‘Ali al-Mainuki.

The U.N. estimates 8,000 to 12,000 Islamic State fighters operate in West Africa, which has become a global center of Islamist militancy.

Write to Michael M. Phillips at Michael.Phillips@wsj.com