NEW DELHI (DPA) - At least 12 one-horned rhinos, a threatened species, have died as a result of flooding in a national park in north-eastern India, park officials said on Sunday (July 21).

Eleven of them drowned while trying to escape floodwaters and one slipped into a ditch while trying to climb a highland, said an official at the Kaziranga National Park in India's north-eastern Assam state.

The sprawling 430-square-kilometre park is a Unesco World Heritage site and home to two-thirds of the world's population of the Rhinoceros Unicornis - more commonly known as the Indian rhinoceros.

At the last count in 2015, the park had a population of 2,401 rhinos.

The recent floods affected about 90 per cent of the park area, forcing the animals to flee to higher ground.

At least 141 wild animals have died since July 13. These include rhinos, an elephant, wild boar and different species of deer, park director P. Sivakumar said.

Most of them drowned, while some were hit by vehicles as they crossed a highway that runs through the park to move to the Karbi Anglong hills.

At least 60 animals had been rescued and most of them released in the wild.

Though the floodwaters have started receding, about 60 per cent of the park is still flooded.

Many of the animals had sought shelter on artificial hillocks built for such situations, Mr Sivakumar said.

India's monsoon season from June to September sees heavy rains which are a lifeline for farmers but often leave a trail of death and destruction.

More than 200 people have died in rain-related incidents in India in July, a bulk of them in Assam and eastern Bihar state.