Vital Kamerhe, a key ally to President Felix Tshisekedi in the Democratic Republic of Congo, was placed in custody at Kinshasa's central prison on Wednesday evening, a judicial source said.
Kamerhe, who became Tshisekedi's chief of staff after a long spell as speaker of parliament, was taken to Makala prison shortly after 7:30 pm (1830 GMT), under a wide-ranging crackdown on corruption.
A key figure on the political scene in the DRC, the 61-year-old Kamerhe was detained under "a provisional arrest warrant" after being questioned for more than six hours by the public prosecutor in an inquiry into suspected mismanagement of public funds, the judicial source said.
It was the first time a presidential chief of staff -- a position that wields great clout in the DRC -- has been arrested in the country's history.
Tshisekedi has vowed to tackle corruption to bring the "renewal" of justice and end the perceived impunity of political and business elites.
Named to head Tshisekedi's cabinet after the new president was sworn in on January 24, 2019, Kamerhe is being investigated into use of funds earmarked for major construction projects.
Kamerhe initially ran in the 2018 presidential elections but backed out to team up with Tshiseki. The two leaders signed a political agreement that gave birth to a joint platform, Heading for Change.
The December 2018 vote led to the first peaceful transition in the history of the former Belgian Congo, although Tshisekedi also has to juggle power with forces that support former president Joseph Kabila.
Kamerhe's political party, the Union for the Congolese Nation (UNC), has several ministers in a sprawling coalition government of 67 members.
A banker, two corporate bosses and an official from a state-owned firm have already been placed in provisional custody during the inquiry into the financing of Tshisekedi's "100 days" action plan. Some detainees have been released.