It is feared that the cubs will not be able to survive on their own in the wild.

“The situation is not easy,” Luciano Sammarone, the director of the Abruzzo, Lazio and Molise National Park (PNALM), said.

“They run away (when approached).”

San Benedetto dei Marsi Mayor Antonio Cerasani called on the public not to do anything that might hinder the search for the cubs.

On Saturday, the two cubs were spotted together and one was later seen on its own, but efforts to capture them, including using traps, have so far failed.

“It gets more difficult to find the two mammals with every day that passes,” Cerasani said.

“I invite everyone to cooperate by not getting in the way of the search and alerting the emergency services to any sightings.

“There is still hope.”

Amarena’s killing has sparked widespread outrage in Italy.

The man who shot the bear, Andrea Leombruni, 56, who is under investigation over the animal’s death, said on Sunday that he had come under a barrage of death threats.

“I haven’t slept or eaten for three days,” Leombruni said.

“I have stopped living. I continually receive telephone calls and messages with death threats.

“They even called my 85-year-old mother.

“My whole family is being pilloried.

“I did the wrong thing,” he continued.

“I realised that as soon as I fired the shot. I was the one who called the Carabinieri police”.

Leombruni’s wife confirmed that the whole family was going through an ordeal.

“This violence is not right, this torture they are putting us through,” she said.

“Prosecutors are investigating and they will judge.

“We will certainly be punished, rightly so, but why do we have to live with police protection? Why should we be afraid to live?”

The PNALM said the bear killing was “unjustified” and had caused huge damage, as it had taken out one of the park’s most prolific females ever, stressing that Amarena “had never caused any type of problem to humans”.

Abruzzo Governor Marco Marsilio described the killing as “incomprehensible”.

Leobruni said he had reacted instinctively after the animal frightened him by appearing on his property.

Avezzano prosecutors have tasked two experts, a vet and a ballistics specialist, with the job of establishing the dynamics of the episode.

WWF Italia said on Friday that it will stand as a civil plaintiff in any case brought against Leombruni.

The organisation’s president, Luciano Di Tizio, said “the killing ... is a crime of an extremely serious and unjustifiable nature, the fruit of a constant campaign of hatred against wild life.

“We will stand as civil plaintiff, but the man responsible risks getting off lightly.

“We need a strong response on everyone’s part.”

ANSA