It follows rumours on social media that the military had been trying to oust the 79-year-old leader, who is currently in the US attending a UN summit with other world leaders.
“The government denies this fake news,” Information Minister Thierry Moungalla posted on X (formerly Twitter) on Sunday, saying he wanted to reassure members of the public they could “go about their activities calmly”.
The government’s website also posted a statement denying the coup attempt reports.
There has been a wave of coups across Africa in recent months, mostly recently in neighbouring Gabon, where the military seized power in August.
Mr Sassou Nguesso rose to power in the oil-producing central African country in a military coup in 1979. He lost Congo’s first multi-party elections in 1992 but regained power in 1997 after a civil war.
The Congolese leader is the third-longest serving president in Africa, after Equatorial Guinea’s Teodoro Obiang Nguema and Cameroon’s Paul Biya.
BBC News