A retired married couple were stabbed to death and dumped in a crocodile-infested river in a South African national park – with cops suspecting they may have been slaughtered for interrupting poachers.

Ernst Marais, 71, and his wife Dina, 73, were found with multiple stab wounds and their hands bound behind their backs early Friday in the Limpopo River within the Kruger National Park.

Their bodies were spotted by a group of horrified tourists who were there to watch a herd of elephants cross the 7,579 square-mile reserve.

The slain couple had trekked more than 1,100 miles from their Mossel Bay retirement village to spend a week at the famous park. There was already a search after they were reported missing on Thursday morning by a maid at their safari camp.

“It was hoped that they had gone off the road and broken down after heavy local floods somewhere but then we got a call to say two bodies had been found,” a national park source said.

“Both had been stabbed in what was clearly a very brutal attack and had been thrown into the river no doubt for the crocs,” the source said, noting that their four-by-four vehicle was also stolen.

“This is a very major incident for us. This is an extremely safe national park and this has shocked us all.”

A South African police source believes the couple may have stumbled into a ruthless group of poachers, who allegedly killed them to stop them from alerting others to their sick operation.

The insider alleges the killers repeatedly knifed the duo in the upper body, tied their hands behind their backs, then dragged them to the driver and dumped them in the water.

“Their pick-up truck would have been an easy way to transport anything they were carrying if they were smugglers and there are unfenced ways to get across the river into Mozambique,” the source said.

“A large manhunt is underway focusing on the assumption they are already out of the Kruger.”

A devastated neighbor said the slaughtered duo loved going on safari and had another home on a wildlife estate near Kruger known as the Valley of the Elephants, which they visited regularly.

She recalled police knocking on the couple’s door Friday morning before their bodies were discovered.

“The police came knocking on their door Friday morning to see if they had returned from Kruger early and then we heard Ernst and Dina had been found dead,” the neighbor said.

“They were a lovely couple who loved going on safari and the residents are all in shock.”