Gunmen in Eswatini killed a prominent opposition politician and human rights lawyer at his home, a spokesman told AFP on Sunday, hours after the country's absolute monarch challenged activists opposed to his rule.

Thulani Maseko was shot dead on Saturday night by unknown attackers in Luhleko, around 50 kilometres (30 miles) from the capital Mbabane, opposition spokesman Sikelela Dlamini said.

He was told that "assassins shot him through the window while he was inside (the) house with his family."

"Details are still scant (and), owing to the trauma his family members are undergoing, they are not yet ready to speak," Dlamini said.

Maseko was a leading human rights lawyer and columnist in Eswatini who had a pending court battle with King Mswati III over the monarch's move to rename the country Eswatini by decree.

The country's name was changed from Swaziland to Eswatini to mark the 50th anniversary of its independence from Britain in 2018.

But Maseko contended that the king did not follow the constitution in the process.

In 2014 Maseko and editor of The Nation magazine Bheki Makhubu were jailed for contempt of court over articles critical of the government and judiciary.

Maseko was the founder of MSF, a coalition of opposition parties, associations and churches.

His death comes just hours after the king challenged activists fighting to end Africa's last absolute monarchy.

King Mswati had said "people should not shed tears and complain about mercenaries killing them".

"These people started the violence first but when the state institutes a crackdown on them for their actions, they make a lot of noise blaming King Mswati for bringing in mercenaries," he said.

Last week, the Swaziland Solidarity Network (SSN) alleged that the king hired mercenaries, mainly white Afrikaners from neighbouring South Africa, to help Eswatini's security forces suppress rising opposition to his oppressive regime.

But government spokesman Alpheous Nxumalo said "no hitmen have been hired".

King Mswati, who has ruled since 1986, is regularly accused of human rights violations.

The king, who can dissolve parliament, the government and appoint or dismiss judges, also commands the police and army.

In June 2021, pro-democracy protests descended into violence resulting in several deaths.