(Bloomberg) -- Salomon Kalonda, a longtime top adviser to Democratic Republic of Congo politician and businessman Moise Katumbi, was arrested at Ndjili airport in the capital, Kinshasa, on Tuesday, Katumbi said on Twitter. 

No reason was given for the arrest, according to Katumbi, who plans to run for president in elections scheduled for December. “The arbitrary & illegal arrest of my special adviser @SalomonKalonda at Ndjili airport is a heinous kidnapping” with “no legal basis,” he said. 

A government spokesman didn’t immediately return a text message requesting comment. Tina Salama, a spokeswoman for President Felix Tshisekedi’s office, said in a text message that the presidency had nothing to do “directly or indirectly” with the arrest. 

Read more: Congo Presidential Hopeful Katumbi Sees Security as Top Priority

Katumbi, the ex-governor of the copper and cobalt-rich province formerly known as Katanga, made his fortune in mining and logistics. He’s also owner of TP Mazembe, one of Africa’s most successful soccer clubs. Kalonda is financial director of the club. 

Human Rights Watch warned on Monday of the possibility of increased political violence as the elections approached.

“As Congo prepares for elections later this year, the government should take all necessary steps to ensure that everyone is able to peacefully express their views without fear of being arrested or beaten by the security forces,” said Carine Kaneza Nantulya, deputy Africa director at the New York-based organization.

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