KINSHASA, Congo (AP) — Congolese President Felix Tshisekedi's government has “serious evidence” of a national security threat, a spokesman said on national television Tuesday night in the first official comments since reports of a failed coup plot emerged.

Presidential spokesman Tharcisse Kasongo Mwema said that investigations were ongoing.

“No attempt to destabilize our democratic institutions will be tolerated,” Kasongo said.

Presidential security adviser Francois Beya was arrested by forces from Congo's National Intelligence Agency last Saturday on suspicion of undermining state security, according to human rights activist Georges Kampiamba.

No details have been released about his arrest, though he was believed to still be in National Intelligence Agency's custody.

The reports were enough to prompt members of the president's political party to demonstrate in front of the Union for Democracy and Social Progress (UDPS) party headquarters in Kinshasa in a show of support for Tshisekedi.

Felix Tshisekedi, the son of the late Congolese opposition political icon Etienne Tshisekedi, won the presidential election in December 2018 after then-President Joseph Kabila did not run for a third term.

It was Congo's first peaceful, democratic transfer of power since independence from Belgium in 1960.

Kabila's party, though, remained influential with a majority in the parliament so a coalition government was formed. However, Tshisekedi dissolved that alliance two years later amid political deadlock and mustered enough support to then sideline Kabila’s party.

Tshisekedi named a new prime minister last February after a Kabila ally who held the post resigned when lawmakers voted overwhelmingly for his ouster.