HeadlineSUICIDE ATTACK STRIKES AFRICAN UNION BASE IN SOMALIA (This article is part of TIMES EXPRESS. It is a condensed version of a story that will appear in tomorrow's New York Times.) MOGADISHU, Somalia -- Somali insurgents mounted a brazen suicide attack against top Somali and African Union officials meeting on Thursday to plan a major offensive in Mogadishu, driving two explosives-laden trucks marked 'U.N.' deep into a fortified base near the airport here and detonating at a fuel depot and the office of an American logistics company, according to witnesses and African Union officials. The attack, which suggested that the insurgents had deeply infiltrated Somali security forces, killed the second in command of the African Union peacekeeping force and seriously wounded several other commanders. 'This was very tactical,' said one peacekeeping official who was not authorized to speak publicly. 'It's like these guys had a map of the place.' Somalia's weak but internationally recognized transitional government is facing intense resistance from insurgent groups linked to Al Qaeda that seem to be increasingly well-schooled in terrorist tactics. The Shabab, Islamist extremists with growing ties to Al Qaeda, claimed responsibility, saying it was in revenge for the American commando strike this week that killed Saleh Ali Saleh Nabhan, a leading Al Qaeda militant. 'We did this,' said Sheik Ali Mohamoud Rage, a Shabab spokesman, adding, 'God helped us.' He accused the Somali government and the African Union of 'planning to launch attacks against us after Ramadan,' the Muslim holy month that ends next week. Heavy machine-gun fire rattled for hours afterward, making it difficult to gain clear information about casualties. Some witnesses said around 15 people were killed. Among the dead was the Burundian deputy commander of the African Union peacekeeping force, Maj. Gen. Juvenal Niyoyunguruza, officials said. Top Somali commanders, including the police chief, were among the wounded. Several Somalis said the U.N. trucks had been stolen in either Baidoa or Jowhar, central Somalia towns that used to have a large U.N. presence but recently under Shabab control. There are around 5,000 African Union troops in Somalia protecting the transitional government. Insurgents have been attacking the peacekeepers relentlessly, often with suicide bombs and roadside explosives. Somalia has been steeped in chaos since 1991, when clan militias ousted the country's last central government and then turned on each other . Many Somali analysts believe the current transitional government, led by moderate Islamists, has the best chance to bring stability in years because it has grassroots support, but its military remains weak and is widely believed to be infiltrated by insurgents, as the attack on Thursday implied. 