The Italian foreign ministry said Luca Attanasio, a carabinieri police officer who was providing security for him and a third person were killed in Goma.
They were travelling in a UN convoy in Congo but the ministry provided no other details.
The Reuters news agency quoting a source from the Virunga National Park said the convoy was attacked during a kidnap attempt near the town of Kanyamahoro at around 10.15am local time (8.15am GMT).
The park had said earlier that two people in the convoy had been killed and the 43-year-old ambassador wounded. The third person killed was a driver, diplomatic sources said.
It was not immediately clear who was behind the attack. There was no immediate claim of responsibility.
Italian newspaper La Repubblica said Virunga rangers immediately launched an operation to free him but he was found dead. His body was taken to the hospital in Goma.
Luigi Di Maio, Italy’s foreign minister, returned to the country early from a trip to Brussels and expressed his “immense pain” at his death.
“The circumstances of this brutal attack are not yet known and no effort will be spared to shed light on what happened,” he said.
“It is with deep sorrow that the foreign ministry confirms the death today in Goma of the Italian ambassador to the Democratic Republic of Congo, Luca Attanasio, and of a policeman from the Carabinieri,” the Italian foreign ministry statement said.
“The ambassador and the soldier were travelling in a car in a convoy of Monusco, the United Nations Organisation Stabilisation Mission in the Democratic Republic of Congo.”
Mr Attanasio, who was married and had three children, had been Italy‘s head of mission in Kinshasa since 2017 and was made ambassador in 2019.
Unverified photos shared on social media showed a UN vehicle with smashed windows along its left side.
Dozens of armed groups operate in and around Virunga, which lies along Congo’s borders with Rwanda and Uganda.
Park rangers have been repeatedly attacked, including six who were killed in an ambush last month.