Numerous questions remain unanswered after Monday's fatal killing of Italy's ambassador to the Democratic Republic of Congo.
Armed assailants in the eastern DRC ambushed a two-vehicle convoy that was travelling to a World Food Programme (WFP) school feeding programme.
Italian Foreign Minister Luigi Di Maio has called on the UN to carry out a full investigation.
He provided parliament on Wednesday with some preliminary details of the attack, but cautioned they remained to be confirmed.
Other information comes from the DRC's presidency and interior ministry and the WFP.
Killed in the attack was Luca Attanasio, 43, Italy's ambassador to the DRC. His 30-year-old Italian bodyguard Vittorio Iacovacci, a member of the Carabinieri police force, was also killed, along with their Congolese driver, Mustapha Milambo, whose age is unknown.
Four WFP staff members also in the convoy survived the attack.
The attack occurred Monday after 10am about 25 kilometres (15 miles) north of Goma, the capital of the North Kivu province that borders Rwanda to the east.
The two-vehicle convoy was headed to Kiwanja, in the Rutshuru territory of North Kivu, but was ambushed about three kilometres (1.8 miles) from their destination.
The road travelled by the two-vehicle convoy runs through a thickly forested mountainous terrain next to the porous border with Rwanda and the Virunga National Park, a UNESCO-listed wildlife reserve.
A vast country the size of continental western Europe, the DRC includes mineral-rich, eastern provinces gripped for decades by militia violence.
According to the office of DRC President Felix Tshisekedi, six attackers armed with five AK-47 assault rifles and a machete ambushed the convoy, forcing it to stop by firing into the air.
The presidency as well as Di Maio, who cites the North Kivu governor, said the assailants then killed driver Milambo in order to force the others into the forest.
Nearby park rangers and army soldiers were alerted by the gunfire and approached the area.
"Five hundred metres (from the site of the ambush), the kidnappers fired point-blank at the bodyguard, who died on the spot, and at the ambassador, hitting him in the abdomen," the presidency said.
No group has come forward to claim responsibility.
The DRC's interior ministry on Monday said the attack was the work of the Democratic Forces for the Liberation of Rwanda (FDLR), a Rwandan Hutu rebel group.
But the FDLR denied this and instead blamed the Rwandan army and Congolese army, saying they had forged "an unnatural alliance to perpetuate the pillaging of eastern DRC."
A US-based monitor, the Kivu Security Tracker (KST), says 122 armed groups were active last year in the country's four eastern provinces of North and South Kivu, Ituri and Tanganyika.
Besides the FDLR, they include the M23, a Congolese Tutsi group also known as the Congolese Revolutionary Army, and the Allied Democratic Forces (ADF), whose stronghold lies near the Uganda border.
Western sources told AFP the attack appeared to be an attempted abduction that went wrong.
Di Maio said Wednesday he expected "clear and exhaustive answers" to Monday's events, including the security arrangements.
The mission to visit the school feeding programme came at the invitation of the World Food Programme, a UN body.
"So even the car journey took place within the organisational framework set up by the World Food Programme," Di Maio said.
The convoy consisted of two 4x4 Toyota Land Cruisers that were not armoured, a diplomatic source told AFP.
The DRC's interior ministry has said the security forces and the provincial authorities had not been informed about Attanasio's trip.
But the WFP has said that the road the convoy travelled on had previously been cleared for travel without security escorts.
Italy's ambassador was "easily accessible and did not bother with protocol. The road was considered safe and did not require a military escort", a European diplomat said.
On Wednesday, the DRC president's office ordered diplomats to report any movements within the country to the government.