KANDAHAR - An elite Afghan soldier shot dead an American mentor and his translator at a US base, Afghan officials said on Friday, in the first rogue shooting blamed on the country's new and closely vetted special forces.

The soldier opened fire at an American military base on Wednesday in Shah Wali Kot district, in volatile Kandahar province, said General Abdul Hamid, the commander of Afghan army forces in the Taliban's southern heartland.

"The shooting took place after a verbal conflict where the Afghan special forces soldier opened fire and killed an American special forces member and his translator," Hamid told Reuters.

At least 18 foreign soldiers have died this year in 11 incidents of so-called green on blue shootings, which are an increasing worry for both NATO and Afghan commanders, eroding trust as Western combat troops look to leave the country in 2014.

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