Guwahati, April 15: The Duke and Duchess of Cambridge, Prince William and his wife Kate, have expressed anguish at the killing of a rhino during their visit to Kaziranga.

The Assam forest department, on its part, admitted that the incident has "nullified" the positive outcome of the royal visit.

The incident occurred at the Burapahar range on Wednesday night, the very day Kate and William had gone on a safari at Bagori range. The couple also petted and fed a rhino calf.

"The Duke and Duchess were angry to hear about the killing of this rhino. They hope their time in Kaziranga encourages others to support the brave rangers protecting animals that are so important to the communities that surround the national park" a spokesman for Kensington Palace said.

"The talks were very positive with the Duke and Duchess and there was hope of some announcement from the Duke. But the incident has completely shattered all that," a senior forest department official told The Telegraph today.

The terrain where the incident took place at Burapahar range is undulating and it is very difficult to know from where the firing started, the official added. Shots were fired from AK-47 rifles.

The park has already lost seven rhinos this year.

Another official said the royal couple were all praise for the staff and the sacrifices made by them for saving wildlife. "They also acknowledged the difficult working conditions," he said.

Assam chief minister Tarun Gogoi today asked additional chief secretary T.Y. Das to probe into the killing of two rhinos in Kaziranga National Park recently and to submit a report immediately. The first incident took place before the royal visit.

Expressing concern over the rhino killings in the past few days, the chief minister asked Das to go into the details leading to the killing of two rhinos and find out who were responsible for protecting those rhinos.

Terming the killings as "very unfortunate", Gogoi asked the special task force to intensify operations against poachers and their accomplices and evolve strategies to tackle poaching by holding discussions with various students', social and community organisations and NGOs involved in wildlife protection.

Earlier this year, CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) had asked India to remain vigilant in its efforts to combat rhino poaching, particularly in Kaziranga.

According to Rhino Task Force report of the National Tiger Conservation Authority, rhino poaching is an organised crime involving national and international gangs, who work in close coordination with one another. It has components of arms smuggling, money laundering, cross-border smuggling, terrorism and international illegal wildlife trade.