The victims, whose bodies were riddled with bullets, included six Americans, a German and two Afghans who were members of the International Assistance Mission in Afghanistan (IAM), a self-described "not-for-profit Christian organisation" that has been offering medical services across the country since the 1960s.
The tenth victim, a British national, worked for the Bridge Afghanistan group.
Both non-profit groups have denied Taliban accusations that their members had been "Christian missionaries".
"She was a humanist and had no religious or political agenda"
"The accusation is completely baseless; they were not carrying any Bibles except maybe their personal Bibles," Dirk Frans, the executive director of IAM, told Reuters. "As an organisation we are not involved in proselytising at all."
The family of the British victim, Karen Woo, also denied that she had been proselytising.
"Her motivation was purely humanitarian. She was a humanist and had no religious or political agenda," the family said in a statement.
General Agha Noor Kemtuz, Badakhshan province's police chief, had earlier said a third Afghan man, who had been travelling with the group, survived.
"He told me he was shouting and reciting the holy Quran and saying 'I am Muslim. Don't kill me'," Kemtuz said.
Nothing left behind
Kemtuz said the survivor told him that the group, which had been travelling in Panjshir, Nuristan and Badakhshan provinces, were surrounded by armed men before they were attacked.
He speculated that robbery could have been a motive in the killings in the remote Kuran Wa Munjan district.
"We couldn't find any passports or anything," he said. "Nothing was left behind."
Violence in Afghanistan is at its worst since US-led and Afghan armed groups overthrew the Taliban in 2001.
June was the bloodiest month of the war for foreign forces in Afghanistan, with more than 100 killed.
Deaths of civilians caught in the crossfire have also risen about six per cent in the first seven months of 2010 against the same period last year, according to the Afghan Independent Human Rights Commission.