COLUMBUS, Ohio (AP) - The Islamic extremist group claiming responsibility for the weekend terrorist attack at a Kenyan mall presents a threat not just to the region or Africa but to "the world at large," the president of Somalia said Monday. President Hassan Sheikh Mohamud said reports that some of the attackers may have been Somalis who lived in the United States illustrate the global nature of al-Shabab. "Today there are clear evidences that Shabab is not a threat to Somalia and Somali people only," Mohamud said in a speech at Ohio State University. They are a threat to the continent of Africa, and the world at large. Kenyan authorities say dozens of people have died in the attack. Mohamud said he has spoken with the president of Kenya and plans to visit the country. Mohamud said his government is committed to uprooting al-Shabab. He said maintaining security is his top priority as Somalia rebuilds after decades of civil war and terrorist threats. But a relapse is a possibility, he warned. In his speech, he called on people from Somalia who are living in Ohio to consider coming home to help rebuilding efforts. Central Ohio has the second-largest number of Somalis in the U.S. after the Minneapolis-St. Paul, Minn., area. The president said his current government has Somalis from the U.S., Australia, Britain, Canada, Sweden and elsewhere. Many more have returned to set up businesses. "The government will prepare the ground for you to come," Mohamud said. The president pledged to continue the policy of creating a unified country bringing together all regions. He also promised free elections in 2016. The key to success, he said, is a country stable in all ways. "Stable in terms of security, stable in terms of politics and stable in terms of economy," Mohamud said. Mohamud started his U.S. visit in Washington, then planned to travel Monday to New York for a speech at the United Nations. Secretary of State John Kerry on Friday praised Mohamud's efforts building a government. "There's work yet to be done in Puntland and Somaliland, and we encourage you to continue the work of reaching out, of reconciliation and rebuilding the democracy, and I know he's committed to that," Kerry added. Outside Monday's university event and at another speech Sunday night, a few dozen Somali protesters challenged Mohamud, saying he was not committed to the constitution or creating a unified country, and he was siphoning too much international aid to the capital of Mogadishu. "We would like him to unify the country, not separate the country," said Liban Abdi, who runs a health care business in Columbus and has lived in the city for 14 years.