 WASHINGTON—Wednesday's attack on a U.S. compound in Afghanistan devastated what has been a hub of counterterrorism and intelligence operations for the spy agency. Seven Central Intelligence Agency officers and contractors were killed and six more wounded in the suicide bomb attack at Forward Operating Base Chapman, CIA Director Leon Panetta said Thursday, the second-largest single-day loss for the spy agency in its history. An experienced CIA debriefer came from Kabul for the meeting, suggesting that the purpose was to gain intelligence, the official said. Taliban spokesman Zabiullah Mujahid said in a statement that an Afghan National Army officer wearing a suicide vest entered the base and blew himself up inside the gym. The suicide bomber who killed seven CIA employees at a remote outpost in southeastern Afghanistan had been invited onto the base and had not been searched, two former U.S. officials told The Associated Press on Thursday 
 
 A former senior intelligence official says the man was being courted as an informant and that it was the first time he had been brought inside the camp. The former intelligence official and another former official with knowledge of the attack spoke on condition of anonymity because they were not authorized to speak publicly. Only four known CIA operatives have been killed in Afghanistan since the 9/11 terrorist attacks in the U.S. 
 
 CIA officer Micheal "Mike" Spann was killed in a prison uprising in November 2001. Six more agency personnel were wounded in what was considered the most lethal attack for the CIA since the war in Afghanistan began in 2001 and possibly even since the 1983 embassy bombing in Beirut. The bombing on Wednesday dealt a blow to the tight-knit spy agency. The base was located in Khost province, a hotbed of militant activity and a stronghold of the Haqqani Network, one of the most hardened and dangerous militant groups, which fought for a decade to wrest the area back from the Russians 
 
 The CIA's Khost base was established in the months after the 9/11 attacks as the U.S. launched its CIA-led offensive against al Qaeda and the Taliban in Afghanistan. "Those who fell yesterday were far from home and close to the enemy, doing the hard work that must be done to protect our country from terrorism," Mr. Panetta said in a message to agency employees. "We owe them our deepest gratitude, and we pledge to them and their families that we will never cease fighting for the cause to which they dedicated their lives _ a safer America." President Barack Obama and CIA Director Leon Panetta were joined by several leading lawmakers on Thursday in praising agency employees for their work. "It's far too early to draw conclusions about something that happened just yesterday," said spokesman George Little. In a letter to CIA employees, Obama said their fallen colleagues came from a "long line of patriots" who had helped to keep the nation safe despite grave risks. Forward Operating Base Chapman used to be a military facility base but was later turned into a CIA base, according to a U.S. official, who spoke on condition of anonymity because he was not authorized to speak publicly. Officials variously said the blast had occurred as the bomber exited a car, or after the bomber had reached the base's gym or its cafeteria. A NATO spokesman said other personnel operate from Chapman as well, but he said he could not elaborate. In a press release Thursday, the Taliban claimed responsibility for the Khost attack.
– Among the seven CIA employees and contractors killed in yesterday's suicide bombing in Afghanistan was the agency's chief officer at the post. One former intelligence official called the attack "devastating" to the CIA's operations in the country. "There was some tremendous talent lost," the official tells the Wall Street Journal. The blast marks grim milestones: It was the deadliest strike against Americans in Afghanistan since October, and it's the first time a suicide bomber struck inside a US facility there. How it happened remains unclear. The AP, quoting anonymous former officials, says the bomber may have been invited to the Chapman military base as a potential informant. He hadn't been searched when he set off the explosives. "Yesterday's tragedy reminds us that the men and women of the CIA put their lives at risk every day to protect this nation," said CIA chief Leon Panetta. Six others were wounded in the blast.