Italy has pressed the United Nations for answers about the attack on a UN food aid convoy in the Democratic Republic of Congo that left a young ambassador and his paramilitary police bodyguard dead.

Foreign minister Luigi Di Maio told politicians in Rome that Italy has asked both the UN and the UN World Food Programme (WFP) to open an investigation into the security arrangements for the convoy, which was attacked two days earlier.

The minister also said Italy will spare no effort to determine the truth behind the killing of ambassador Luca Attanasio and military police officer Vittorio Iacovacci. A WFP Congolese driver, Moustapha Milambo, was also killed in the attack.

“We have formally asked the WFP and the UN to open an inquest that clarifies what happened, the motivations for the security arrangements employed and who was responsible for these decisions,” Mr Di Maio said.

The trip was undertaken at the UN’s invitation, according to Mr Di Maio.

The two Italians had “entrusted themselves to the protocol of the United Nations”, which flew them on a UN plane from Kinshasha to Goma, (1,500 miles away, Mr Di Maio said.

The Italian embassy in Kinshasha, Mr Di Maio noted, has two armoured vehicles at the ambassador’s disposal for moving around the city and the country. But for Monday’s mission, to visit a WFP school food project in Rutshuri in eastern Congo, Mr Attanasio was traveling in UN vehicles.

Only hours earlier, Mr Di Maio, flanked by Premier Mario Draghi, met the arrival of the bodies of the two Italians at a Rome military airport. A state funeral for both men was set for Thursday in Rome.

A special team of investigators, dispatched by Rome prosecutors, arrived on Tuesday in Congo on what Mr Di Maio said would probably be multiple missions to determine what happened.

Mr Attanasio, 43, who leaves a widow involved in volunteer projects in Congo and three young children, “was in love with his profession, with Africa and his family”, Mr Di Maio said. He noted that the police officer was nearing the end of his security detail in Congo and was soon due back in Rome.

The World Food Programme, which won the Nobel Peace Prize last year for its efforts to feed refugees and other malnourished people worldwide, is headquartered in Rome.

The WFP said the road had been previously cleared for travel without security escorts. UN security officials based in Congo usually determine road safety. On Tuesday, UN spokesman Stephane Dujarric said in New York that the UN had launched an internal review concerning the “security around the incident”.

Mr Di Maio said the attackers numbered six, had light arms and apparently spread obstacles on the road and fired shots in the air to stop the convoy.