MOGADISHU (Reuters) - Four Somalis were killed when a car bomb hit a United Nations convoy near the capital's international airport on Wednesday, showing the threat still posed by insurgents despite their recent loss of territory.
Al Qaeda-aligned Somali Islamist group al Shabaab claimed responsibility.
The group, which wants to topple the Western-backed Mogadishu government and impose its version of Islamic law, damaged a U.N. vehicle but did not kill any U.N. staff, a spokesman for the U.N.'s Somalia mission, Aleem Siddique, said.
Somali police said four Somalis were killed in the explosion, including a policeman and two bodyguards working for a contractor. Thirteen other people were wounded.
Attacks have intensified in recent weeks, showing the threat still posed by al Shabaab after African peacekeepers pushed them out of the capital in 2011. Officials say the Islamists still control tracts of countryside and settlements from where they have launched their guerrilla-style campaign.
The militants have in the past used car bombs against the U.N., African Union troops and other international delegations.
Al Shabaab's spokesman for military operations, Sheikh Abdiasis Abu Musab said in a statement the bomb had "targeted a convoy of foreign mercenaries and their apostate allies".
Security around the airport was increased after the attack but airport operations and its flight schedule were unaffected, the prime minister's communications team said on Twitter.
The airport has a tight security cordon and blast walls, and is used as a base for U.N. operations in Somalia. The airport area also houses the British and Italian embassies.
International delegations visiting Mogadishu frequently travel with local security firms which place pick-up trucks at the front and back of a convoy, each with about 10 security men armed with AK-47 rifles.
Also on Wednesday, in neighboring Kenya, a court charged 13 people with being members of al Shabaab after they were arrested during police raids in mosques in the port city of Mombasa.
Al Shabaab said it killed 28 people outside Mandera, a town in the far northeast near the Somali and Ethiopian borders, in retaliation for the raids on the mosques.
The group also said it was responsible for killing 36 non-Muslim workers at a quarry on the outskirts of Mandera on Tuesday as part of its efforts to force Kenya to pull its troops out of Somalia.
Unions have urged thousands of non-Muslim Kenyan teachers, doctors and nurses living in the northern regions to return home because of the security risks.
Writing by Drazen Jorgic; Editing James Macharia and Louise Ireland