The Russian-led International Boxing Association (IBA) on Wednesday cancelled a ban on amateur boxers from Russia and Belarus and said it would allow them to compete with national flags and anthems in events with immediate effect.
The world governing body, which is at odds with Olympic organisers, said in a statement that its board of directors had voted in favour of the change.
Russian energy company Gazprom is the biggest sponsor of the IBA, formerly known as AIBA.
"The IBA strongly believes that politics shouldn't have any influence on sports. Hence, all athletes should be given equal conditions," it said, adding that it remained "politically neutral and independent.
"IBA calls for peace and remains a peacemaker in any conflicts. Moreover, the IBA has obligation to ensure equal treatment towards the athletes and competition officials, regardless of their nationality and residence," the statement said.
"Both Russian and Belarus teams will be able to perform under their flags, and the national anthems will be played in case they win a gold medal.
"According to the decision, the technical officials of Russia and Belarus will also be back in the competitions."
Athletes, referees and judges from both countries have been barred since March from the IBA's international competitions, following Russia's February invasion of Ukraine.
The IBA, led by Russian businessman Umar Kremlev, last month suspended Ukraine ahead of a meeting that decided not to hold a fresh presidential election.
The IBA does not recognise Kyrylo Shevchenko as president of the Ukrainian federation but instead considers its head to be Volodymyr Prodyvus, a Kremlev ally who left Ukraine in February.
Kremlev was quoted last week as saying the time had come for athletes from Russia and ally Belarus to be allowed to compete under their own flags.
The IOC has taken away from the IBA the qualification tournaments and the competitions at the Paris 2024 Olympics after also stripping the boxing body in 2019 of its involvement in last year's Tokyo Games due to governance, finance, refereeing and ethical issues.
Boxing has also not been included in the initial programme for the 2028 Los Angeles Games.