Afghanistan : President Barack Obama has vowed a swift probe into the killing of 16 Afghans by an American soldier as he called his counterpart Hamid Karzai to express shock over the incident, which has sparked fresh tensions after the burning of copies of the Quran at a US-run military base.

Obama, who telephoned Karzai on Sunday night, “extended his condolences to the people of Afghanistan, and made clear his administration’s commitment to establish the facts as quickly as possible and to hold fully accountable anyone responsible,” the White House said in a statement.

Obama called Karzai to express his “shock and sadness” over the killing of 16 civilians, mostly women and children.

He “reaffirmed our deep respect for the Afghan people and the bonds between our two countries,” the statement said.

Before speaking to Karzai, Obama had issued a statement describing the Kandahar incident as “tragic and shocking”, which did not represent American values.

“This incident is tragic and shocking, and does not represent the exceptional character of our military and the respect that the US has for people of Afghanistan,” he said.

“I am deeply saddened by the reported killing and wounding of Afghan civilians. I offer my condolences to the families and loved ones of those who lost their lives, and to the people of Afghanistan, who have endured too much violence and suffering,” Obama said.

US-Afghan ties had plunged to an all-time low last month after the burning of copies of Quran at the American-run military base in Bagram, an incident which triggered anti-US protests across Afghanistan which left around 40 people dead.

US Defence Secretary Leon Panetta also called Afghan President Karzai to express his condolences.