The president of Somalia's Olympic committee and the head of the national football federation were killed in a suicide bomb blast Wednesday that the IOC called an "act of barbarism."
FIFA President Sepp Blatter said he knew both men personally and they would be "sorely missed."
Somali Olympic Committee head Aden Yabarow Wiish and Somali Football Federation chief Said Mohamed Nur were among at least 10 people killed after a female suicide bomber detonated a bomb at the newly reopened national theatre in Mogadishu during a ceremony also attended by top government officials.
The explosion happened as Somali Prime Minister Abdiweli Mohamed Ali was standing at a podium to deliver a speech. The prime minister was unharmed, said government spokesman Abdirahman Omar Osman.
The International Olympic Committee said it was "shocked to hear of the terrorist attack" that killed two of Somalia's sports leaders.
"Both men were engaged in improving the lives of Somalian people through sport and we strongly condemn such an act of barbarism," the IOC said in a statement. "Our thoughts are with the Somalian sporting community who lost two great leaders and with the families of the victims."
Blatter said his thoughts were with the football and sporting "family" in Somalia.
"I knew both men personally and can only say good things about their endless efforts to promote sport and football in their country. They will be sorely missed," the FIFA president said.
African Football Confederation president Issa Hayatou sent condolences to the families of those killed.
"It is another black day for African football. It's a tragedy as Somali football lost a great leader … who was actively committed to football development despite very challenging conditions."
Somali sport was rocked by at least two terrorist attacks last year. In October, Somali Football Federation general secretary Said Arab and a national team player were hurt when a car bomb killed 57 people in Mogadishu.
Earlier in 2011, an under-20 international player was killed in a blast and two teammates were injured when they were walking home from a training session.
Wednesday's attack came with the country's Olympic committee preparing for the London Games, which start on July 27. Somalia has sent athletes to the last four Summer Games despite violence and instability at home.
The national football team has struggled and did not enter the qualifying competition for next year's African Cup. It has already been eliminated from qualifying for the 2014 World Cup.