In Rabat, Morocco's Foreign Ministry denounced the statement, posted on the Internet, as "barbarous" and "contrary to Islam precepts and the fundamental values of the humanity".
The al Qaeda group said on Tuesday it would put the two Moroccans, driver Abderrahim Boualam and assistant Abdelkrim El Mouhafidim, on trial. The two were seized late last month.
"The legislative authority of al Qaeda organisation in Iraq has decided to carry God's law against the infidels and has ruled to kill them," the al Qaeda group said on Thursday. "After the court looked into the detainees' case, it was proven, without any doubt, that they are followers of the despots (US) and infidel Moroccan government.
The group has warned Arab and Muslim governments against sending envoys to Baghdad, saying such a move recognises what it says is an infidel government allied with the United States.
The statement could not be verified, but it was posted on an Islamist Web site often used by Abu Musab al-Zarqawi's group. It was not clear when the killings would be carried out.