Eswatini received $5.1 million from the US government under a deal to accept third-country nationals deported by the Trump administration, its finance minister said on Tuesday.

Eswatini is among several African nations that agreed to receive third-country deportees as part of President Donald Trump's crackdown on illegal immigration. Others include South Sudan, Ghana and Rwanda.

Details of the agreements have not been disclosed, and Eswatini's government is facing a lawsuit from human rights lawyers who claim the secretive deal was unconstitutional.

Finance Minister Neal Rijkenberg confirmed the $5.1 million figure in a text message but declined to give further details, saying the transaction was handled by the prime minister and that he was unaware of it until afterwards.

At least 15 immigrants sent to Eswatini from US

Reuters has seen an unverified copy of the agreement which both governments have so far declined to comment on.

The document, signed on May 14 in Eswatini's capital Mbabane, said that the US would provide Eswatini with $5.1 million to "build its border and migration management capacity" and that in exchange, Eswatini would accept up to 160 third-country deportees.

"We have no comment on the details of our diplomatic communications with other governments," a US State Department spokesperson said, adding that implementing the Trump administration's immigration policies was a top priority.

The US has sent at least 15 immigrants to Eswatini so far, from countries including Vietnam, Cuba, Laos, Yemen and the Philippines. They are imprisoned there, except for one who was repatriated to Jamaica.