FDLR is an armed rebel group active in the eastern Democratic Republic of the Congo.
In a statement made available to APA, authorities in Kinshasa promised to open investigations to flush out the killers.
"A convoy of the World Food Program (WFP) was the target of an ambush laid by armed gangs comprising of fighters of the Democratic Forces for the Liberation of Rwanda (FDLR), on the road to Rutshuru, Kibumba groupement, in the territory of Nyiragongo", reads part of the statement.
The Italian ambassador to Congo, Luca Attanasio and an Italian Carabinieri police officer were killed Monday while travelling in Congo in a UN convoy, the Italian Foreign Ministry said in a separate statement.
The convoy was attacked near the town of Kanyamahoro at around 10:15 am (0815 GMT) and was part of a kidnap attempt, the Virunga National Park said.
The envoy, Luca Attanasio, "died of his wounds" after a convoy of the UN's World Food Programme (WFP) came under fire near Goma, the source said in Kinshasa.
Two other people also died in the attack, Major Guillaume Djike, the army's spokesman in North Kivu province said, without identifying the casualties.
Since 1994, The eastern Democratic Republic of the Congo (DRC) has been mired in violence for two decades and continues to be plagued by dozens of armed groups.