Its report comes after days of controversy in Zambia, with Mr Lungu's critics questioning how he acquired the land and the cost - unconfirmed reports have put the mansion's price tag at around $4m (£3m).

Zambia's chief government spokeswoman Dora Siliya has not commented about the price, but has said that King Mswati gave Mr Lungu the land as a "gift". "These are normal practices when the president travels, that various gifts are given in various forms. In this case it was land that was given to the president. This land was processed and given to the president in title,” Ms Siliya told a press briefing earlier this week.

“So there is nothing sinister about that because I do know now that people like to create stories even when there are no stories.”

But there are doubts that King Mswati owned the land.

The Times of Swaziland reports that despite the Zambian government saying the land was a gift, it had seen documents from the Deeds Registry which showed that it was one of around 90 plots owned by Inyatsi Properties Limited, which had acquired it lawfully from Rudolph Investments last year.

Retired Zambian presidents were by law entitled to a house constructed by the state as part of their retirement package. Mr Lungu, however, scrapped off the entitlement three years ago as a “cost-saving” measure.