A Belgian zoo said Saturday it will shorten its rhinos' horns as an anti-poaching measure following the grisly killing of a white rhino in France this week.

A four-year-old southern white male was shot three times in the head at a French zoo in Thoiry outside Paris on Monday and had its horns cut off probably "with a chainsaw" police said.

The perpetrators, who have still not been found, stole only the main horn, which is estimated to be worth 30,000-40,000 euros ($32,000-$42,690).

The Pairi Daiza zoo, about 60 kilometres (40 miles) southwest of Brussels, has three adult rhinos and a baby white rhino born in March 2016 as part of its 5,000-animal complex.

Director Eric Domb wrote on the zoo's Facebook page that the French killing had prompted him to ask "our veterinarian to proceed on a temporary basis and as an additional measure to security procedures already in place at Pairi Daiza" to shorten their rhinos' horns.

"This heinous act is the first in Europe but it is part of a long line of rhino horn thefts from many European museums," Domb wrote.

With this measure, he said, he also wanted to not only protect the zoo's animals but its security personnel as well.

In the Thoiry incident, intruders forced the main gate of the zoo and broke through at least two other security barriers before shooting dead the rhino, called Vince.

The killing marked the first time a European zoo had been breached in that way.

Investigators believe the murder was part of an organised trafficking ring.

Black market rhino horn sells for up to $60,000 per kilo -- more than gold or cocaine -- with demand principally coming from China and Vietnam where it is coveted as a traditional medicine and supposed aphrodisiac.

One horn can weigh four kilos -- comprised exclusively of keratin, the same substance in human hair and fingernails.

"Depending on circumstances, this measure could be renewed," Domb wrote. "Frequently used in many national African parks, it is considered today as one of the only effective deterrents."

Wild rhino numbers are plummeting. About 1,400 are killed every year, out of an estimated population of 25,000 -- mainly in South Africa but also in Asia and India.

Source: AFP