An aide to Afghan President Hamid Karzai who is under investigation for corruption is on the payroll of the Central Intelligence Agency, The New York Times reported Wednesday. Citing unnamed Afghan and US officials, the newspaper said Mohammed Zia Salehi, the chief of administration for Afghanistan's National Security Council, had been receiving money from the US intelligence service for years. The revelation raised new questions about how the US can root out corruption in the Afghan government when US operations in the country require support from some of the same politicians and leaders accused of graft. Salehi was arrested in July after Afghan police said a wiretap caught him soliciting a bribe in exchange for holding up a US investigation into a company suspected of moving money for Afghan leaders, drug traffickers and insurgents. He was released after just seven hours in prison, after Karzai intervened on his behalf. Meanwhile, Karzai said that US plans to start withdrawing troops from Afghanistan next year had boosted the Taliban's spirits, while an insurgent attack killed eight Afghan police in the country's increasingly volatile north Thursday. Speaking to a visiting US congressional delegation, Karzai said the July withdrawal date had provided “morale value” to the insurgency, the presidential office said. Karzai also told the head of US Central Command, Gen. James Mattis, that terrorism could not be defeated without rooting out terrorist sanctuaries across the border. More than 10 militants attacked the police checkpoint outside the northern city of Kunduz, said provincial police chief Abdul Raziq Yaqoubi, adding they suspected the attackers were jihadists from Russia's restive Chechnya region who are active in the surrounding province, also called Kunduz. He said two or three of the militants were wounded when the police fought back. The militants apparently hoped to steal the policemen's weapons but were beaten back before they could do so, he said. Afghanistan drills oil Afghanistan, believed to be sitting on top of billions of dollars worth of minerals and energy sources, has extracted oil for the first time and plans to pump a modest 800 barrels a day, officials said Thursday. Afghanistan's Mines Ministry plans to open bidding soon for contracts to refine the oil from the rugged Sar-i-Pul province in the north. “The infrastructure existed there a long time ago. We overhauled them and this is the first time we are extracting oil,” said Jawad Omar, a spokesman for the ministry.