Four French troops were shot dead by a man dressed as an Afghan soldier in eastern Afghanistan on Friday, an Afghan official said. \"A man wearing Afghan army uniform opened fire on French nationals, killing four and injuring 16 others this morning in Tagab district of Kapisa province,\" the security official told AFP on condition of anonymity. A spokesman for NATO forces said earlier four NATO troops were killed and the shooter had been arrested, but did not give the nationality of the troops.