The US has deported 10 people to Eswatini despite rights groups in the southern African state mounting legal action to block the plan.

This is the second batch of deportees that the Trump administration has sent to Eswatini as part of its hard-line approach towards immigration.

The 10 have been securely accommodated, and posed no threat to the public, Eswatini's prison department said in a statement.

Eswatini accepted five deportees, described by the US government as deprived monsters, in July. One of them has since been repatriated to Jamaica, his country of origin, while another two were expected to be repatriated soon, Eswatini's government says.

In a statement on Sunday, the government said it would take in 11 deportees following an agreement with the US to cooperate in this manner. It did not explain why only 10 had arrived. Their names have not been made public.

In an earlier statement, acting spokesperson Thabile Mdluli said the deportees would be kept in a secured area separate from the public, while arrangements are made for their return to their countries of origin.

Their arrival comes a day before a court case against the deportations is set to resume in the main city, Mbabane. The Southern African Litigation Centre (SALC) - along with other civil society groups - argues that the government's decision amounts to executive over-reach and Eswatini's constitution states that such agreements should be done with parliamentary consent, something that did not happen in this instance.

Activists also protested against the deal outside the US embassy. The civic groups say the deal is secretive and an example of democratic regression, 20 years after Eswatini adopted a constitution to give more of a say to parliament in a country where the king has long wielded absolute power.

Some MPs had previously raised concern about the deal in parliament, but Prime Minister Russell Dlamini said it had been handled at top clearance level.

The deal also alarmed neighbouring South Africa, which expressed fears that the deportees could cross into the country via their porous border. Ms Mdluli tried to allay the fears by saying the deportees were being held in solitary confinement in a secure facility.

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