Namibian authorities stepped up an anti-poaching alert Monday after announcing that 28 rhinoceros had been killed by poachers since the start of the year, including 19 at the country's largest animal reserve.

The southern African country's environment ministry said an "urgent high-level meeting" with security officials had been called to plan measures to combat the "barbaric" poaching wave.

The ministry also appealed for public help "in this difficult fight" against a phenomenon surging again across southern Africa. No arrests have been made so far, the ministry added.

Namibia's Etosha Park has been particularly hard hit by the new wave of killings.

Of the 19 rhinos slaughtered in the park, 10 were found during a campaign in March to dehorn rhinos to reduce the risk of them becoming poaching targets, the ministry said.

The horns are used in traditional medicine in Asian markets after the animal is killed.

"This is our flagship park and has a high concentration of rhino conservation and other high value species making it a major attraction of tourists," the ministry said in a statement.

Authorities said 87 rhinoceros were killed across Namibia in 2022, up from 45 the previous year. Figures for 2023 have not yet been revealed.

In neighbouring South Africa, which has the highest population of rhinoceros, nearly 500 were killed by poachers last year, up 11 percent from 2022.

There were an estimated 23,300 rhinoceros in Africa at the end of 2022, with about 15,000 in South Africa.