US President Donald Trump on Sunday said the US military could deploy troops to Nigeria or carry out air strikes to stop what he called the killing of large numbers of Christians in the West African country.

Asked if he envisioned troops on the ground or air strikes in Nigeria, Trump told reporters aboard Air Force One: "Could be. I mean, other things. I envisage a lot of things. They're killing record numbers of Christians in Nigeria ... They're killing the Christians and killing them in very large numbers. We're not going to allow that to happen."

Trump made the comment on Sunday evening as he headed back to Washington after a weekend at his vacation home in Florida.

Trump threatened on Saturday to take military action against Nigeria if Africa's most populous country failed to crack down on the killing of Christians.

Earlier on Sunday, Nigeria said it would welcome US help in fighting Islamist insurgents as long as its territorial integrity is respected.

Daniel Bwala, an adviser to Nigerian President Bola Tinubu, also sought to play down tensions between the two states, despite Trump calling Nigeria a "disgraced country."

"We don't take it literally, because we know Donald Trump thinks well of Nigeria," Bwala said.

"I am sure by the time these two leaders meet and sit, there would be better outcomes in our joint resolve to fight terrorism," he said.

Nigeria, a country of more than 200 million people and around 200 ethnic groups, is divided between the largely Muslim north and mostly Christian south.

Islamist insurgents such as Boko Haram and Islamic State West Africa Province have wrought havoc in the country for more than 15 years, killing thousands of people, but their attacks have been largely confined to the northeast of the country, which is majority Muslim.

While Christians have been killed, the vast majority of the victims have been Muslims, analysts say.

"Insurgent groups such as Boko Haram and Islamic State West Africa often present their campaigns as anti-Christian, but in practice their violence is indiscriminate and devastates entire communities," said Ladd Serwat, senior Africa analyst at US crisis-monitoring group ACLED.

The group's research shows that out of 1,923 attacks on civilians in Nigeria so far this year, the number of those targeting Christians because of their religion stood at 50.

Serwat said recent claims circulating among some US right-wing circles that as many as 100,000 Christians had been killed in Nigeria since 2009 are not supported by available data. (Reuters)