A car bomb went off outside Mogadishu airport Thursday killing four members of the Somali security forces and two civilians, police said.The 19 wounded, all Somalis, included members of the security force and civilians, officials said. The United Nations said the attack targeted one of its convoys, damaging one UN car and lightly injuring four security escorts with the convoy. No UN staff was injured, said Nicholas Kay, Special Representative for Somalia.Police said the attack was a suicide bombing. Several cars went up in flames as the bomb was triggered at the main entrance. Security forces fired stray bullets to prevent further attacks.The Islamist group al-Shabaab claimed responsibility for the attack.“Several enemy members have perished,” al-Shabaab member Sheikh Ali Mohamed Hussein said on the pro-insurgent Radio Andalus.Information Minister Mustafa Dhuhulov condemned the attack as “cowardly.” UN Secretary General Ban Ki-moon also condemned the attack.“The secretary general remains determined to support the Somali government in preventing such attacks and holding the perpetrators accountable,” said Martin Nesirky, a spokesman for Ban.