Luca Attanasio, 43, was shot dead on Monday after unidentified assailants ambushed a two-vehicle convoy from the UN's World Food Programme (WFP) in the eastern North Kivu province, near the Rwanda border.

The ambassador's bodyguard from Italy's Carabinieri police forces, Vittorio Iacovacci, 30, and a Congolese WFP driver, Mustapha Milambo, 56, were also killed. Six others survived the attack.

"Luca was betrayed by someone close to us, to our family," Attanasio's wife, Zakia Seddiki, told Italian newspaper Il Messaggero.

"Someone who knew his movements has spoken, has sold him out and betrayed him," she said without giving more detail as investigations are under way.

Attanasio, who had been Italy's chief diplomat in Kinshasa since 2017, lived in the capital with Seddiki and their three daughters. He was given a state funeral in Rome on Thursday, and was due to be buried in his home town of Limbiate, near Milan, on Saturday.

Meanwhile, the La Stampa daily said Attanasio had in 2018 asked his ministry to double his embassy security detail from two to four Carabinieri officers, but his request was denied.

According to La Stampa, the previous ambassador had four Carabinieri. The Italian foreign ministry did not immediately respond to a request for comment on the report.

The WFP said Thursday that three separate investigations have been launched into Monday's attack -- by the UN's security department, as well as by Italian and Congolese authorities.

According to Congolese and Italian authorities, the convoy was ambushed three kilometres (two miles) from its destination, the town of Kiwanja, where the UN convoy was due to visit a school.

After shooting Milambo, six assailants with AK-47s assault weapons forced the occupants of the two vehicles to follow them into the Virunga National Park, a wildlife reserve.

When nearby rangers and Congolese soldiers alerted by the gunfire approached the assailants, Attanasio and Iacovacci were shot.

DRC authorities accused the Rwandan Hutu rebels of the Democratic Forces for the Liberation of Rwanda (FDLR), who have denied any involvement and instead blamed members of the Rwandan and Congolese armies.