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An air strike hit a refugee camp in southern Somalia, killing at least five people and wounding 45, most of them children, an international aid agency said Monday. Kenya's military acknowledged carrying out an air raid but said it targeted only Islamist militants.

Details emerged, meanwhile, about an American-Somali man who al-Shabab said carried out a suicide attack against an African Union base in the Somali capital, Mogadishu, on Saturday. Abdisalan Hussein Ali was 19 at the time he disappeared from Minnesota, which has a large Somali-American community, in November 2008.

In July 2010, he was among several men indicted in a long-running investigation in Minnesota. Charges against him included conspiracy to provide material support to a foreign terrorist organization and conspiracy to kill, maim, kidnap and injure. The U.S. hasn't yet confirmed the identity of the bomber. FBI spokesman Kyle Loven in Minneapolis said the agency is using DNA to try to make a positive identification.

A Somali Islamist militant group used the casualties from the Kenyan air strike as a recruitment tool to try to win even more recruits. Kenyan military spokesman Maj. Emmanuel Chirchir, though, blamed an al-Shabab fighter for the civilian deaths, saying an al-Shabab fighter drove a burning truck of ammunition into the refugee camp in the town of Jilib where it exploded.

Chirchir said the Kenyan air force hit the truck on Sunday as it drove away from an al-Shabab training camp and accused the driver of attempting to use the refugees as a human shield. He said 10 al-Shabab members were killed and 47 wounded in the attack, citing informers on the ground.

But Doctors Without Borders, also known as Medicines Sans Frontieres or MSF, said the aerial bombardment hit the camp for displaced people. MSF said it treated 52 wounded people. As of Monday morning, MSF confirmed five deaths and said it was still treating 45 wounded, 31 of them children. Seven other patients had been discharged after receiving treatment. The head of the MSF mission in Somalia, Gautam Chatterjee, said most of the wounded had shrapnel injuries.

Jilib town elder Ahmed Sheik Don said the planes hit a bus stop and near the camp before finally hitting a base of al-Shabab, an insurgent group linked to al-Qaida.

It was impossible to immediately reconcile the different versions. Either way, civilian casualties would be a public relations issue for Kenya and could turn ordinary Somalis against Kenya's military intervention in the lawless nation.

Residents said hundreds ran for cover Sunday as bombs exploded. The town's population has ballooned this year as about 1,500 families fled to the area amid a famine that has wracked the south. Residents reported that al-Shabab fighters were among the casualties.

Sheik Abukar Ali Aden, an al-Shabab official in southern Somalia, said the militants donated food to those affected by the airstrikes. Bearded men and masked fighters used megaphones to ask Somalis to join their militant group.

"I am urging all Muslims in the Jubba regions to raise their heads and defend themselves against the enemy massacring them," Aden said at a news conference in the southern port town of Kismayo. "Go! go to the front lines and make jihad with the Christian enemy."

Kenya sent troops across the border into Somalia in mid-October following cross-border kidnappings blamed on gunmen from southern Somalia.

Somali Prime Minister Abdiweli Mohamed Ali said his government is looking into the airstrike and reports of civilian deaths.

"If it has taken place then it is an unfortunate incident and we are sorry about that," Ali said during a press conference in Nairobi alongside Kenyan Prime Minister Raila Odinga.

Odinga added: "Our troops have not targeted civilians. It would be most unfortunate."

The U.N. representative for Somalia, Augustine P. Mahiga, said civilians must be protected during any party's military operations. He said the U.N. hopes that Kenya's push into southern Somalia will help gain access to famine victims.

"We think this in the end will contribute to the sum total of gaining more territory, greater security and therefore more access to the victims of famine and drought, especially in south-central Somalia," Mahiga said.

The Danish Refugee Council, meanwhile, said it has made its first contact with an American aid worker and her Danish colleague who were kidnapped last week in northern Somalia.

"It has been some very long days as we have been waiting for signs of life. It is truly a relief that we now have received the message that they are as well as possible their circumstances taken into consideration," said Ann Mary Olsen, the head of the Danish Refugee Council's International Department.

Olsen said the aid agency is appealing to traditional leaders and clan elders to help release the hostages.

Somalia has not had a functioning government since 1991. African Union troops have been engaged in fierce fighting in Mogadishu to push al-Shabab from its last base in the city. On Saturday, the Islamists launched an attack with two suicide bombers, killing at least 10 people.