Sudan's ousted president Omar Hassan al-Bashir says he received millions of dollars from Saudi Arabia, a police detective told a Khartoum court on Monday, Reuters reports.

AFP reports that the former president, who was forced from power by months of protests in April, sat in a metal cage wearing a traditional white gown at the opening of his corruption trial.

His relatives chanted "Allahu Akbar" (God is greatest) as proceedings got under way. Bashir arrived in a huge military convoy.

Bashir is charged with illicit possession of foreign currency and accepting gifts in an unofficial manner, Reuters says.

Local news website Radio Dabanga says Bashir himself has not commented on the charges - but his team of defence lawyers has dismissed them as 'baseless'.

Police Brigadier General Ahmed Ali Mohamed, a detective in the team investigating Bashir, testified that Bashir told them he had received $25 million from Saudi Arabia's Crown Prince Mohammed Bin Salman, known as MbS.

Reuters quotes the detective as saying that Bashir said MbS gave him the money for spending outside the Sudanese state budget and that it was spent on donations, without going into further details on who received it.

AFP reports that Bashir said he also received two previous payments of $35 million and $30 million from Saudi King Abdullah, who died in 2015.

Radio Dabanga reported in April that a substantial amount of cash was seized during a search of Bashir's residence in Khartoum.

Bashir has been indicted by the International Criminal Court in The Hague on charges of masterminding genocide in Sudan's Darfur region.

The Saudi government communications office did not immediately respond to a request from Reuters for comment on the testimony.

The next hearing is scheduled for Saturday.