Frank-Walter Steinmeier, Germany's foreign minister, said he felt "deep sadness and horror" at the deaths, while Javier Solana, European Union foreign policy chief, denounced the attack.
"I condemn in the strongest possible terms this terrorist act," he said in a statement from Brussels.
A British man working for ArmorGroup, a private security firm, was also shot dead in Kabul on Wednesday, the British foreign office and his company said.
The attacks came as the US army said its soldiers and Afghan forces attacked al-Qaeda positions in the second day of an air and ground assault in the mountainous Tora Bora region.
Captain Vanessa Bowman of the US army said on Wednesday: "US and Afghan forces engaged al-Qaeda and other violent extremist fighters in eastern Afghanistan during a combined arms assault using precision munitions.
"The targets were carefully chosen to pinpoint enemy positions and eliminate the likelihood of harming innocent civilians."
Scores of civilians fled the area to escape the assault, Afghan media reports said.
Tora Bora, which lies about 50km south of the eastern city of Jalalabad, was the scene of a US-led operation in December 2001 to capture Osama bin Laden, al-Qaeda's leader.
The area, a complex of caves, in known as the last stronghold of al-Qaeda in Afghanistan.
The 1996-2001 Taliban government gave shelter to al-Qaeda and allowed it to operate training camps within Afghanistan.