Burundi's former intelligence chief, General Adolphe Nshimirimana, was killed in a drive by shooting and rocket attack in the capital Bujumbura, a presidential spokesman said.
General Nshimirimana was killed by gunmen in a car, who fired automatic weapons at Nshimirimana's vehicle and shot it with two rockets, witnesses and police told AFP.
In April, mass demonstrations broke out after President Pierre Nkurunziza announced he was seeking a third term in office, with Burundian security forces violently suppressing protests.
Nshimirimana was widely seen as a key member of Nkurunziza's security team.
The presidency's communications chief, Willy Nyamitwe, confirmed the death on Twitter. "I have lost a brother, a companion in the struggle. The sad reality is that Gen Adolphe Nshimirimana is no longer with this world," he said.
Nkurunziza was re-elected on July 21, amid allegations of electoral fraud and the violent intimidation of opposition by the country's security forces.
Around 100 people have been killed in anti-government protests. Nshimirimana is believed to have played a key role in foiling the coup in May.