Yevgeny Prigozhin, the head of the Wagner Group, has allegedly died in an aircraft accident.
About ten persons on board were also killed in the private jet disaster.
According to reports, a suspected Russian military force shot down the private plane in the Tver region, north of Moscow.
Meanwhile, President Putin issued a short statement through video link to the summit in Johannesburg.
He thanked South African President Cyril Ramaphosa for hosting the summit and for the expansion of the group beyond the current five nations.
He did not comment on last night’s plane crash.
This comes after the Brics group decided to invite six countries – Argentina, Egypt, Iran, Ethiopia, Saudi Arabia and the United Arab Emirates – to become new members of the bloc.
Russian Foreign Minister Sergei Lavrov has been representing Putin in South Africa and was at the press briefing. However, he did not address attendees.
Yevgeny Prigozhin was the head of the Wagner mercenary group, which he established in 2014.
He was once a wealthy businessman with a criminal record; and he was also known as “Putin’s chef” because he provided catering for the Kremlin.
In June, he led his troops on a short-lived mutiny, after they seized control of the southern Russian city of Rostov-on-Don and moved towards Moscow, with the stated aim of removing the military leadership.