The two Japanese diplomats and their Iraqi driver who were gunned down in northern Iraq were ambushed by assailants in three or four vehicles, two witnesses said Tuesday.

The assailants' cars surrounded the diplomats' four-wheel-drive vehicle Saturday on a highway near Tikrit and fired into its left side, apparently with automatic rifles, they said.

While it remains unclear who the assassins are, the witnesses' reports raise the likelihood they had targeted the diplomats.

Further reinforcing this theory, Senior Vice Foreign Minister Ichiro Aisawa said Wednesday in Tokyo the attack was probably the work of terrorists and not bandits, because the victims' cash and credit cards were not touched.