GUAHATI, India — Rising floodwaters have inundated large parts of a famous wildlife reserve park in northeastern India, killing more than 225 animals and forcing hundreds of other animals to flee, the park director said Saturday.

Around 15 rhinos, 185 deer and at least one Royal Bengal tiger have died in the devastating floods that have submerged almost the entire Kaziranga National Park in Assam state, Satyendra Singh said.

“Carcasses of animals were seen floating in the floodwaters. It’s a heartbreaking scene,” Singh said.

Meanwhile, across northern India and neighboring Nepal and Bangladesh, the death toll from drowning, collapsed houses and landslides triggered by annual monsoon rains climbed to around 578 on Saturday.

Army soldiers and disaster management workers in the three countries have launched mammoth rescue efforts to evacuate and provide food and shelter to the nearly 16 million people affected by the floods in South Asia.

In the northern Indian state of Bihar, at least 153 people died as swirling floodwaters submerged hundreds of villages and swept away homes made of mud and straw.

Eleven million people have been affected by the floods in 17 districts of the state, said Pratay Amrit, an official in Bihar’s disaster management department. Nearly half a million people were in more than 1,300 state-run relief camps, where they were being provided rice and lentils and medical care, he said.

In neighboring Uttar Pradesh state, the death toll rose to 40 as floodwaters submerged entire villages after 13 small dams were washed away, state officials said.

The Rohini, Gandak and Rapti rivers were flowing above the danger mark and could breach their banks, adding to the sense of urgency in evacuating people from low-lying villages, said Avnish Awasthi, a government spokesman.

The flood situation worsened after water was released from swollen rivers in Nepal that threatened to overflow, Awasthi said.

Soldiers used motorboats to rescue people marooned on rooftops while air force helicopters dropped packets of food and drinking water to those trapped in their homes.

Officials said 144 people were swept away or drowned in Assam while 60 others were killed in West Bengal state.

At Kaziranga, nearly 80 percent of the 430-square-kilometer (250-square-mile) wildlife park was under water. Some of the animals had crossed a highway and moved to higher land. The Assam government has deployed security guards on the highway to protect the rhinos from poachers, said Singh, the park director.

In Nepal, floods have killed around 110 people since the monsoon rains began in June. However, the floodwaters were receding and no new casualties have been recorded, officials said.

In Bangladesh, more than 70 people have died over the past week due to drowning or snake bites this monsoon season.

The government’s Flood Forecasting and Warning Center said Saturday that the flood situation was expected to continue to improve over the next few days.

Many flood protection embankments and dikes have collapsed because of the force of the floodwaters across the impoverished northern region of Bangladesh, a delta nation of 160 million people that’s crisscrossed by more than 130 rivers.