US President Donald Trump has ordered the preparation of plans for military action in Nigeria to tackle Islamist militant groups, accusing the government of not doing enough to halt the killing of Christians.

Trump did not specify which killings he was referring to, but claims of a genocide against Nigeria's Christians have been circulating in recent weeks and months in some right-wing US circles.

Groups monitoring violence say there is no evidence to suggest that Christians are being killed more than Muslims in Nigeria, which is roughly evenly divided between followers of the two religions.

The government of Africa's most populous nation has not responded to the threat of US military action.

However, Nigeria's President Bola Tinubu insisted that there was religious tolerance in the country and said the security challenges were affecting people 'across faiths and regions'.

Trump wrote in a social media post on Saturday that he had instructed the US Department of War to prepare for 'possible action', warning that he might send the military into Nigeria 'guns-a-blazing' unless the Nigerian government intervened, adding that all aid to the country would be cut.

Trump stated: 'If we attack, it will be fast, vicious, and sweet, just like the terrorist thugs attack our CHERISHED Christians!'

He declared Nigeria a 'Country of Particular Concern' due to the 'existential threat' to its Christian population, claiming 'thousands' have been killed without providing evidence.

This designation allows for sanctions against countries engaging in severe violations of religious freedom.

Following Trump's announcement, Tinubu stated that his government is committed to working with the US and the international community to protect communities of all faiths, insisting that the characterization of Nigeria as religiously intolerant does not reflect the national reality.

Jihadist groups such as Boko Haram and Islamic State West Africa Province have caused turmoil in north-eastern Nigeria for more than a decade, mostly affecting Muslims according to violence analysis groups. In central Nigeria, clashes occur frequently between mostly Muslim herders and farming groups who are often Christian over access to water and pasture.

Trump, despite previous claims of peace through his tenure, faces mounting pressure from right-wing voices regarding Nigeria's evolving religious landscape and violent conflicts.