Afghan shootings: Hillary Clinton's 'regret' over rogue soldier

US Secretary of State Hillary Clinton has expressed her "deepest regret and condolences" after a US soldier went on the rampage killing 16 Afghans.

She said: "I cannot imagine the impact on the families".

The Pentagon said in a media briefing that the killings, in the early hours of Sunday, were "tragic" but insisted it was an isolated incident.