(CNN) -- A young Somali woman set off a bomb blast that rocked Somalia's newly reopened national theater in the capital city Wednesday, killing two top sports officials, a Somali U.N. official said.
Six people died in the explosion and several -- including Prime Minister Abdiweli Mohamed Ali -- were injured, Omar Jamal told reporters in New York.
Said Mohamed Mugambe, head of the Somali football federation, and Somali Olympic committee chief Adan Hagi Yabarow Wish were two of those killed in the attack.
The bomb went off during a celebration for the first anniversary of Somali national television in Mogadishu, according to witnesses. Screaming people fled the theater, and the sound of ambulance sirens filled the air.
Jamal said the bomb, which exploded when Ali was on the stage, was intended to kill the prime minister and other high-ranking officials.
Ali suffered minor injuries but remains determined to bring security to the country, he said.
"Again the prime minister this morning confirmed his commitment, so did the president, that they will continue making sure that the country will be stabilized," Jamal said.
He said the young woman, who was very skinny and appeared to be aged 20 to 25, had been acting suspiciously before the event but was carrying a police ID, which was "part of the reason she was able to get in."
The African Union Mission in Somalia (AMISOM) earlier said the device had been detonated by a female suicide bomber who blended in with the crowd gathered for the occasion.
The attack on a high-profile event in the heart of the capital is seen as a big symbolic blow to Somalia's attempts to reinvent itself on the international stage after years as a failed state.
Sepp Blatter, president of football's governing body FIFA, said he was shocked by the news of the two sports officials' deaths.
"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," he said.
FIFA's vice president, Prince Ali, also extended his condolences to the victims' families. "We have faith that the football family is resilient and will continue promoting the values of peace and coexistence through our beautiful game," the Jordanian prince said.
The Islamist group Al-Shabaab, which has been waging war against Somalia's weak transitional government, claimed responsibility for the bombing via Twitter.
A post to the group's Twitter page said the explosives had been planted before the gathering and denied that a woman had carried out the attack.
Brig. Gen. Audace Nduwumunsi, deputy force commander of AMISOM, condemned the bombing.
"We are united with the Somali government and stand firm together. This was a despicable crime against the Somali people, but it will not stop us achieving peace in Somalia," he said.
"Yet again the terrorists' methods show that they are enemies of peace and are foreign to Somali culture. By their attack, they are trying to derail the hopes and dreams of the Somali people, but they will fail."
He urged anyone in Mogadishu with information about planned attacks to come forward.
The Islamist group announced in February that it was tightening its ties to al Qaeda and has long been considered a terrorist movement by the United States.
It has waged an insurgency against the feeble Transitional Federal Government since 2007 but has suffered recent setbacks in its heartland in southern Somalia.
AMISOM and government forces drove Al-Shabaab fighters from the center of Mogadishu last year, while Kenyan troops crossed into southern Somalia in October to hit back for a rash of kidnappings it blamed on the group.
But despite their efforts, Al-Shabaab has continued to launch terror attacks in the capital.
Last month, it claimed responsibility for an attack in which a suicide bomber detonated his explosive at a tea shop near Somalia's presidential palace, killing two people.
A report released by the UK-based Royal United Services Institute think tank Wednesday highlights how al Qaeda is seeking to reinvigorate and expand its operations by strengthening ties with established Islamist groups such as Al-Shabaab.
Al-Shabaab is also increasingly working to recruit members from outside Somalia, the report says, presenting a new challenge for Western nations.
"The group has sought to expand its recruitment network by tapping into the pool of foreign jihadists and radicalised individuals in the Middle East, Europe and the US," author Valentina Soria writes.
However, this may be a sign of waning domestic support in the face of military operations and food shortages, she says, and there is no evidence so far that it will lead to attacks by Al-Shabaab on targets overseas.
World leaders met in London in February to address terror and conflict in the Horn of Africa nation and seek ways to resolve other critical problems, including famine and weak leadership.
CNN's Nima Elbagir and Gavino Garay contributed to this report.