In a post on Truth Social, the US president called IS "terrorist scum" and accused them of "primarily targeting and brutally murdering innocent Christians."
He said the US military carried out "multiple precision strikes," but provided no further details.
It is unclear which targets were struck or when the attack took place.
In November, Trump ordered the US military to prepare for action against Islamist militant groups in Nigeria. In his post late Thursday, Trump said that "under my leadership, our country will not allow radical Islamic terrorism to flourish."
In his November warning, the US president did not specify which killings he was referring to. However, in recent months, claims of a genocide against Christians in Nigeria have been circulating in some right-wing circles in the US.
Organizations that monitor violence say there is no evidence to support the claim that Christians are being killed at a higher rate than Muslims in Nigeria. Nigeria's population is roughly evenly divided between followers of the two religions.
No evidence of increased attacks on Christians
Earlier, an adviser to Nigerian President Bola Tinubu told the BBC that any military action against jihadist groups should be carried out jointly.
https://timesindian.com/news/england-beat-australia-in-fourth-ashes-test-first-win-in-15-years
Daniel Bwala, a special adviser to Nigerian President Bola Tinubu, said Nigeria would welcome US assistance in dealing with Islamist militants, but also stressed that Nigeria is a "sovereign" country.
He also said that the jihadists are not targeting people of any particular religion. President Tinubu has insisted that religious tolerance exists in the country and that security challenges are affecting people of "all faiths and regions."
Earlier, Trump had declared Nigeria a "country of particular concern," claiming that the country's Christian population was under threat and that "thousands" had been killed, although he provided no evidence to support this claim.
In central Nigeria, there have also been frequent violent clashes between predominantly Muslim herders and farming communities, who are often Christian, over access to water and grazing land.
Thousands have been killed in this cycle of retaliatory attacks, but atrocities have been committed by both sides.
Human rights organizations say there is no evidence that Christians have been specifically targeted.
