Police in the US state of Ohio shot dead dozens of lions, tigers, bears and wolves in a frantic hunt Wednesday after the owner of an exotic farm freed the dangerous animals and then killed himself.

The bloody toll -- which included 18 endangered Bengal tigers -- sparked outrage from conservationists and calls for restrictions on the largely unregulated ownership of exotic pets.

Sheriff Matt Lutz defended his shoot-to-kill order, telling reporters that officers were in a race against the oncoming darkness when they arrived at the farm around 5:30 pm (2130 GMT) Tuesday and saw the wild predators running free.

"Public safety was our number one concern," Lutz said. "We are not talking about your normal, everyday house cat or dog."

He praised the bravery of the men who left their squad cars to confront the animals armed only with handguns, but said he wished they never had to face such a terrible choice.

"These killings were senseless. For our guys to have to do this, it was crazy," Lutz said.

"We don't go to the academy and get trained on how to deal with 300 pound Bengal tigers. I'm just glad they had the courage to get out of their cars."

Game wardens, SWAT teams, and experts from the nearby Columbus Zoo were called in to assist with the hunt as night fell and residents were warned to stay in their homes.

But they only had four tranquilizer guns -- which carried drugs that can sometimes take a while to put a large animal to sleep -- and couldn't risk losing the animals in the dark or the woods.

One "very aggressive" tiger was shot dead on Wednesday morning when it went "crazy" and started to run towards nearby woods after it was shot with a tranquilizer, Lutz said.

"We could not have animals running loose in this county. We were not going to have that," he added.

Of the 56 animals set loose, only six were captured alive: a grizzly bear, three leopards and two monkeys.

The other slain animals included two wolves, six black bears, two grizzly bears, nine male lions, eight lionesses, one mountain bear and a baboon.

At least one of the animals was struck by a vehicle on a nearby highway and the mauled body of a monkey was also recovered.

A monkey that might be infected with Herpes was still unaccounted for, but may also have been eaten by one of the lions.

The animals were buried on the 73-acre farm Wednesday.

It is a "tragedy" that the animals died but officials had no other choice, said Jack Hanna, director emeritus of the Columbus Zoo and the host of an animal television show.

"I'm sorry that this had to be done but if you had 18 Bengal tigers running around in these neighborhoods, you folks would not have wanted to see what happened," Hanna, who helped to organize the hunt, told reporters.

The remaining animals were taken to the zoo but were expected to eventually be returned to the estranged wife of Terry Thompson, 62, who was found dead in the driveway.

Ohio has few laws governing the ownership of exotic animals, but Hanna said he was working with the governor's office to enact regulations to try and prevent a repeat of the tragedy.

Ohio Congressman Dennis Kucinich issued a statement urging swift passage of a bill restricting the ownership of exotic animals, noting that there have been 22 incidents in the state involving such animals since 2003 including the death of a man last year while feeding a pet bear.

A spokesman for Governor John Kasich told AFP that a task force already working on new rules for exotic animals is expected to have legislation ready within 30 days and defended the decision to shoot-to-kill.

"The safety of the populace has to be the paramount concern -- period," spokesman Rob Nichols told AFP.

Local news reports said federal agents raided the farm in June 2008, seizing more than 100 guns, and that Thompson had previously been fined for letting his animals wander.

But WWF Tiger expert Leigh Henry said the fact remained that people "can go buy a tiger in Ohio" or in seven other states that have no requirement for any kind of license or permit to do so.

"I would say the current patchwork of laws in the United States regulating these captive tigers is inexcusable," she said.

Born Free USA, an animal protection group, said the death of so many animals should be a call to action against private ownership.