Inexperienced operators of a US drone aircraft ignored or downplayed signs that Afghan civilians were in a convoy blasted in a deadly American missile attack earlier this year, a military report released Saturday said. At least 23 people were killed in the Feb. 21 attack in Uruzgan province. It was the deadliest missile strike for Afghan civilians in six months and occurred as NATO forces were redoubling efforts to avoid killing innocents. The attack prompted a strong rebuke from Afghan President Hamid Karzai and a quick apology from the commander of US and NATO forces in Afghanistan, Gen. Stanley McChrystal, who is struggling to gain the broad support among Afghans. The insurgents claimed a victory Saturday when they captured a government outpost in a remote mountainous region near the Pakistan border. Jamaludin Badar, governor of eastern Nuristan province, said government forces withdrew from the district headquarters in Bargi Matal early Saturday after a major assault by Taliban militants and a battle lasting several days. Fighting was still going on and Afghan forces hoped to recapture the district center with the help of NATO airstrikes, Badar said. He could not provide casualties. Taliban spokesman Zabiullah Mujahid claimed in a phone message sent to reporters that insurgents had taken complete control of the district, captured three police vehicles and forced security forces to flee road checkpoints. North of the capital, a senior Taliban leader in Baghlan province was killed in a NATO airstrike late Friday, the international force said in a statement. It said the man, who was not named, was the Taliban's “shadow governor” of the region and was responsible for organizing and directing attacks on coalition forces. In the civilian deaths case, attack helicopters fired missiles and rockets into the convoy on a main road near Khod village, where US Special Forces and Afghan troops were battling militants at the time, a summary of the investigation said. Commanders judged that the convoy contained fighters heading toward the village to reinforce the militants. Meanwhile, a suicide attacker with explosives strapped to his body blew himself up Saturday outside a military caterer in Kabul but caused no casualties, Afghanistan's interior ministry said.