PESHAWAR: Suspected militants killed a tribal elder in South Waziristan for allegedly "spying" for the United States, officials said on Thursday. Noor Muhammad was gunned down late on Wednesday in Angoor Adda, 40 kilometres west of Wana, said administration officials on condition of anonymity. Noor, 44, had been receiving threatening letters for the past few months, accusing him of "spying" on militants on both sides of the Pak-Afghan border for the US-led coalition, his family told reporters. One letter, said his cousin, had warned: "Stop spying for US forces in Afghanistan or you will be killed." This is the second such execution to have taken place in the area this week. On Monday suspected militants, believed to have links to the Taliban, beheaded a tribesman in North Waziristan on similar charges.