The US has deported five people who it described as "criminal illegal aliens" to the southern African kingdom of Eswatini.

On board the flight were five deportees from Vietnam, Jamaica, Laos, Cuba and Yemen who have been convicted of crimes ranging from child rape to murder, US Homeland Security Department Assistant Secretary Tricia McLaughlin said in an online post.

"This flight took individuals so uniquely barbaric that their home countries refused to take them back," McLaughlin wrote on X.

Eswatini, the last absolute monarchy in Africa, said it acknowledged "widespread concern" within the country regarding the deportations.

"Five inmates are currently housed in our correctional facilities in isolated units, where similar offenders are kept. The nation is assured that these inmates pose no threat to the country or its citizens," government spokesperson Thabile Mdluli said in a statement.

Eswatini and the US will work with the United Nation's immigration agency to "facilitate the transit" of the deportees to their country of origin, Mdluli added.

Earlier this month, the US sent eight migrants from several countries to South Sudan after a court lifted restrictions on sending people to countries where they have no ties.

In a series of posts on the X social media platform, McLaughlin listed the crimes the five deported to Eswatini had been convicted of, describing them as "depraved monsters" who had been "terrorizing American communities".

"A safe third country deportation flight to Eswatini in Southern Africa has landed," she said, adding: "They are off of American soil".

The Eswatini government declined to say whether any payments were made as part of the arrangement.

The US is the fourth largest market for the country's biggest export, sugar. Analysts suggest that Eswatini may be trying to safeguard this trade and avoid the imposition of tariffs.

A pro-democracy group, the Swazi Solidarity Network, has condemned the deal as deplorable.

Spokesperson Lucky Lukhele told the BBC that Eswatini must not become a dumping ground for criminals, and that citizens needed protection.

The news has sparked public concern over whether local prisons are equipped to securely house such inmates.

Previously known as Swaziland, Eswatini is a small, landlocked country that is surrounded by South Africa and Mozambique. It has been led by King Mswati III since 1986.

Last month, the US Supreme Court cleared the way for the Trump administration to resume deporting migrants to countries other than their own.

Rwanda has confirmed discussions have taken place, while Benin, Angola, Equatorial Guinea and Moldova have also been named in media reports as potential recipient countries.

Trump's administration has already deported people to El Salvador and Costa Rica.

South Sudan recently agreed to hold eight men deported from the US and said they were not in handcuffs and appeared to be in good condition.

The war-torn country said the deportees were kept in a civilian facility in the capital Juba, under the watch of police and the national security service. Only one of them is from South Sudan.

In April, US Secretary of State Marco Rubio revoked all visas for South Sudanese passport holders blaming the country for failing to accept the return of its repatriated citizens in a "timely manner".

It is not clear if that has now changed.

Last week, Nigeria said it would not bow to pressure from the Trump administration to accept Venezuelan deportees or third-country prisoners from the US.

President Donald Trump's pledge to conduct mass deportations was a centrepiece of his election campaign and an issue on which he drew widespread support, including many Hispanic voters.

He said he wanted to deport people living in the US illegally but White House efforts have been much broader in scope - taking aim at people in the US on student visas, suspending admissions of refugees except white South Africans, and moving to revoke temporary work permits and other protections that had been granted to immigrants by previous presidents.

To crack down on immigrants, Trump's administration has resumed raids at workplaces, a tactic that had been suspended under his predecessor, Joe Biden.

Additional reporting by Nomsa Maseko