Four rhinoceros have been brutally killed by poachers in flood-hit Kaziranga National Park (KNP) since Tuesday, including one on Thursday, prompting an alarmed Assam government to ask for a CBI inquiry into it and post army in the fringe areas.

Terming as 'shocking' the killings of the endangered animal as, Union Environment Minister Jayanthi Natarajan ordered a probe by a team of Wildlife Crime Control Bureau (WCCB) officials and sought a report within a week.

"I am shocked.... Unscrupulous poachers have exploited the situation of natural disaster (floods) and attacked helpless animals which were seeking shelter. I have ordered a probe by a team of Wildlife Crime Control Bureau (WCCB) officials," she said.

Assam Chief Minister Tarun Gogoi, who returned from Japan on Thursday, told reporters here that the state government would recommend to the Centre a CBI inquiry into the killing of rhinos by poachers during the past three years. He also announced cash reward of Rs 5 lakh to anyone providing information about the poachers.

KNP director Sanjay Bora said poachers killed one female rhino at Dolamara range along the Karbi hills in the early hours of the day and removed its horn, considered an aphrodisiac and also used in traditional medicine.

A male rhino, who had strayed from the flooded park, was found shot inside Jagadamba tea estate bordering Bagori range of the Park with its horn removed, Bora said adding the animal is struggling for its life and a veterinary team has rushed to the spot to treat it.

Another female rhino left bleeding on Wednesday by poachers, who shot it, sawed off its horn and cut off a part of its right ear, died during the day. The carcass of another rhino with its horn removed was found at the Kaziranga National Park.

Forest Minister Rakibul Hussain told reporters here that army personnel would be deployed in the fringe areas of KNP to prevent poachers from escaping after committing the crime. He said, all measures have been taken to protect the rhinos but poachers were taking advantage of the flood, which had submerged 80 per cent of KNP.

"We have taken steps to equip forest department personnel with sophisticated weapons and more forest guards will be deployed soon to deal with the situation," he said.

Hussain said the government had decided to create the post of chief conservator of forests to head KNP administration and has appointed senior forest official N.K. Vasu to the post. The post of the Director has also been upgraded to conservator of forests.

He appealed to the organisations who have launched protests against rhino killings to desist from taking the law into their hands and not take any step that would demoralise the frontline staff of the Park.

There has been an increase in wildlife population in the Park mainly due to efforts of the forest personnel and local people living in the vicinity, he said and urged all people living in the fringe villages to cooperate with forest officials in protecting the rhinos from the poachers.

Poachers have so far killed 16 rhinos this year and the attacks have sparked protests by All Assam Students Union, Asom Jatiyatabadi Yuba Chatra Parishad and Krishak Mukti Sangram Parishad, who blocked NH 37 passing by the side of KNP.

The demonstrators burnt effigies of Chief Minister Tarun Gogoi and state forest minister Rockybul Hussain. ULFA anti-talk faction too condemned the killing of rhinos and accused the state government of failing to save Assam's heritage.

"The state government and its forest department have failed to protect the rhinos and now it is the duty of the people to take necessary steps to protect the animal," a statement e-mailed by the outfit to the media said.