Devastating floods in northeast India have killed around 600 animals in the region's largest wildlife park, including more than a dozen threatened one-horned rhinos, officials said Monday.

"Most of the animals either drowned or were mown down by speeding vehicles when they tried to flee the heavy flooding," said S.K. Bora, director of 430-square-kilometre (165-square-mile) Kaziranga National Park in Assam state.

"The water level is now receding, but the vast majority of animals that fled the park are yet to return," he told AFP by telephone.

According to Bora, various species of deer accounted for more than 500 of the animal victims, which also included 14 rhinos and two elephant calves.

Assam has been the focus of severe regional flooding in recent weeks, triggered by heavy monsoon rains that caused the Brahmaputra river to burst its banks, inundating large areas of the state.

Nearly 130 people have been killed and six million displaced by the floodwaters, according to official figures.

Kaziranga is home to the world's single largest population of one-horned rhinos. A 2012 census in the park counted 2,290 of the rhinos, out of a global population of 3,300.

The species declined to near extinction in the early 1900s, and is currently listed as "vulnerable" by the International Union for Conservation of Nature.

Kaziranga has fought a sustained battle against rhino poachers, who kill the animals for their horns, which fetch huge prices in some Asian countries where they are deemed to have aphrodisiac qualities.

Assam Forests Minister Rockybul Hussain voiced concerns that poachers would prey on those rhinos that had been forced out of the protective ring of the park by the flooding.