Congo's president has condemned a French investigation into alleged embezzlement by him and Gabon's leader as "racist" and "colonial".
Denis Sassou-Nguesso is thought to own several houses in France
"In France, all the world's leaders have castles and so on. I am very surprised that only two people are targeted," said Denis Sassou-Nguesso.
The complaint was made by three groups, which claim that properties in France were bought with stolen funds.
Gabon's Omar Bongo Ondimba has also reportedly angrily denied the charges.
Both countries are oil exporters.
Mr Sassou-Nguesso said he would have ignored the complaint had it not been linked to racism and colonialism.
The properties include flats linked to Mr Sassou-Nguesso's family in Paris's Foch Avenue, in Parisian suburbs such as Courbevoie and Velizy, and in expensive areas in the south of France such as the Cote d'Azur, the BBC's Catherine Zemmouri in Paris says.
President Bongo has also dismissed the charges
The three groups making claims against the two leaders were Survie (Survival), which has criticised France's support of African dictators in the past, an international network of legal experts called Sherpa and the Federation of Congolese from the Diaspora.
Survie wants the properties to be seized and sold, with the proceeds being used to build schools and hospitals in Africa.
"The properties never belong directly to presidents themselves but instead to their daughters, sons, nephews or [are] registered to property companies," Benjamin Mutsila, president of Congolese Diaspora, told the BBC.
"It is not a president's salary that could have generated the considerable resources needed to acquire such property," said lawyer William Bourdon, president of the Sherpa group, quoted by the AFP news agency.
Mr Bongo, 71 and Africa's longest-serving head of state, won re-election last year for another seven-year term.
He has ruled the oil-rich country since 1967.
Mr Sassou-Nguesso, 63, ruled Congo from 1979 to 1992, and then returned to lead the country after a coup in 1997.