The carcasses of 18 wolves have been found in an Italian national park within the space of a week in an apparent series of poisonings described by conservationists as the most serious crimes against wildlife in Italy in a decade.

Authorities of the national park of Abruzzo, Lazio and Molise said eight wolves were found dead in recent days in three different areas of the vast park, adding to the 10 carcasses discovered last week. Three dead foxes and a buzzard were also found.

“The disappointment blends with despair … It’s a pain that ranges from profound suffering to disbelief,” the national park’s authorities said in a statement. “We hope that we don’t have to deal with further bad news. We repeat once again that whatever the motivation, illegality and crime cannot be justified in any way.”

A criminal investigation began last week after suspected poisoned bait was found by park rangers in the vicinity of five dead wolves in the Alfedena area, leading to suspicions that five other wolves found in Pescasseroli died in the same way.

Tests are being done to determine how the animals died although park authorities said the simultaneous deaths of other animal species pointed strongly to deliberate poisoning.

The situation is especially worrying given the presence of the marsican bear, a critically endangered subspecies of the brown bear, across the Apennine mountains of the national park.

Luciano D’Angelo, the prosecutor leading the investigation, told Corriere della Sera last week: “Bears and wolves are symbols of this area and we do not take their killings lightly. Initial investigations tell us it was poison, but we’ll know later exactly what it was.”

The Italian unit of the World Wildlife Fund (WWF) said the suspected wolf killings were the “most serious crimes against wildlife of the last 10 years” and marked “an unacceptable criminal trend in a civilised country”.

“We’ve reached 18 [wolves] illegally killed within just a few days,” the organisation said. “This continued massacre strikes at the heart of our natural heritage. Spreading poison to target an iconic species like the wolf is a cowardly and criminal act against biodiversity and an attack on public safety – it’s 2026 and these acts cannot go unpunished.”

WWF Italy partly blames the deaths on the EU last year downgrading a wolf’s status from “strictly protected” to “protected” in a move mainly aimed at allowing easier culling and management of growing populations. The downgrade came after pressure from farmers owing to an increase in attacks on livestock, and was strongly backed by European commission president, Ursula von der Leyen, because a wolf killed her beloved family pony, Dolly.

There are an estimated 20,000 wild wolves across EU countries. The majority are in Italy, followed by Romania, Bulgaria, Greece, Poland and Spain.

In Italy, hunting wolves, which used to be classified as “harmful pests”, was once actively encouraged. But in the 1970s, when their population almost became extinct, the Italian government passed a law giving them official protection and banning wolf hunting.