Security forces shot dead six Taliban in a southern Afghan district overrun by rebels last week, while a coalition soldier and a tribal chief were killed elsewhere, officials said on Friday. The Dutch forces in the southern province of Uruzgan meanwhile told a news agency in The Hague they have killed at least 18 enemy fighters over the past 10 days. The six rebels were killed in Helmand province's southernmost Garmser district on the border with Pakistan in a security sweep over the past two days, provincial spokesman Moheedin Khan told AFP.The Garmser headquarters was invaded by dozens of Taliban late on Monday causing the under strength police force to flee. Afghan and US-led coalition troops entered and secured the town early Wednesday with little resistance. The security forces late Tuesday secured adjoining Naway-i-Barakzayi after its district headquarters was also briefly overrun. The Taliban claimed responsibility for the killing a tribal chief in Helmand's Musa Qala district who was shot dead Thursday by two men on a motorbike, Khan said.