Eight people from different African countries have been deported to Uganda from the United States, the first of such transfer under a migration deal signed last year.

The group arrived on Wednesday after a US judge approved their cases, Uganda's foreign ministry said.

The ministry said in a statement that its deal with the US designated Uganda as a safe third country for migrants who cannot return to their countries, for reasons such as persecution.

The Uganda Law Society has condemned the deportations, saying the individuals had effectively been dumped in the country "through an undignified, harrowing and dehumanising process". 

The organisation called the process illegal and said it would challenge it in court.

The BBC has asked the US Department of Homeland Security for comment.

US President Donald Trump's administration has deported dozens of people to third countries since coming into power last January - part of its hard-line approach towards immigration.

Human rights campaigners have condemned the policy, with some questioning its legality.

Uganda's foreign ministry said it could not give many details about the deportees for privacy reasons, but said: "Uganda continues to uphold its longstanding commitment to providing sanctuary to persons in need and assuring they are treated with dignity."

It said they were neither Ugandan nor US citizens but were "of African origin who may not be granted asylum in the USA and are reluctant to or may have concerns about returning to their country of origin".

The BBC's US partner CBS News reports that Uganda agreed to accept deported migrants as long as they did not have criminal histories.

According to the US, many of those transferred to other third countries have been convicted criminals.

Since the start of his second term, Trump has embarked on sweeping efforts to remove undocumented migrants - a key election promise that drew mass support during this campaign.

Uganda is among several African countries which, as a third country, have accepted deportees from the US. These include Eswatini, Ghana and South Sudan.