The leader of an attempted coup on Sunday in the Democratic Republic of Congo (DRC) has been killed and some 50 people including three American citizens arrested, a spokesman for the Central African country's army told Reuters.

Gunfire rang out around 4 a.m. in the capital Kinshasa, a Reuters reporter said. Armed men attacked the presidency in the city centre, according to spokesman Sylvain Ekenge.

Another attack took place at the nearby home of Vital Kamerhe, a member of parliament who is tipped to become speaker, Kamerhe's spokesman, Michel Moto Muhima, and the Japanese ambassador said in posts on X.

Moto Muhima said two guards and an attacker had been killed in that incident. Ekenge also said one attacker was killed there.

A shell fired from Kinshasa hit the city of Brazzaville in neighbouring Republic of Congo, injuring several people, that country's government said in a statement, adding that one person had been hospitalised.

Ekenge named Christian Malanga, a U.S.-based Congolese politician, as the leader of the attempted coup.

"Malanga was definitively neutralised during the attack on the Palais de la Nation, a certain Aboubacar was neutralised during the attack on the residence of Vital Kamarhe [and] the others - around 50 including three American citizens - were arrested and are currently undergoing interrogation by the specialised services of the Armed Forces," Ekenge told Reuters.

He said Malanga first attempted and aborted a coup in 2017 and that one of the American citizens arrested was Malanga's son.

A Facebook page appearing to belong to Malanga posted a live-streamed video of what appeared to be the attack.

"We, the militants, are tired. We cannot drag on with Tshisekedi and Kamerhe, they have done too many stupid things in this country," Malanga said in Lingala in the video, which has not been independently verified by Reuters.

U.S. Ambassador Lucy Tamlyn said in a post on social media that she was "very concerned" by reports that American citizens had allegedly been involved in the events.

"Please be assured that we will cooperate with the DRC authorities to the fullest extent as they investigate these criminal acts and hold accountable any U.S. citizen involved in criminal acts," she said.

The U.S. embassy had earlier issued a security alert warning of "ongoing activity by DRC security elements" and reports of gunfire in the area.

The United Nations' stabilisation mission in the DRC said that its chief, Bintou Keita, condemned the incidents in the strongest terms and offered her support to the Congolese authorities in a post on X.

Tshisekedi was re-elected for a second term as president in December, but has yet to name a government, six weeks after appointing a prime minister.

Kamerhe was a candidate for speaker of parliament in an election that had been scheduled for Saturday but was delayed by Tshisekedi.