The US state of Ohio came under pressure Thursday to quickly regulate the trade in "exotic" animals after dozens of lions, bears and rare tigers freed by their suicidal owner had to be killed.

Less than 24 hours after police announced the slaughter, nearly 28,000 people had signed an online petition, posted by an Ohio resident, urging Governor John Kasich to ban the sale and ownership of wild animals.

"Ohio has some of the most lax regulation of exotic pets, and after this disaster, it is apparent that this lack of regulation has been a threat to public safety and the welfare of the animals for too long," it said.

A spokesman for Kasich said Wednesday that work was already under way to ban the sale or importation of exotic animals in Ohio and that legislation should be tabled in about 30 days.

"We think the legislature will move very quickly on it," spokesman Rob Nichols told AFP.

Animal rights activists said that is not soon enough, and that emergency regulations ought to be immediately implemented in Ohio and other states.

"If legislation had been in place with regards to exotic animal this would never have happened," said Delcianna Winders, director of captive animal law enforcement with People for the Ethical Treatment of Animals (PETA).

Bears, lions, tigers, wolves and monkeys ran amok when owner Terry Thompson, 62, flung open the enclosures at his Muskingum County animal farm near the town of Zanesville on Tuesday evening and then shot himself.

Police following shoot-to-kill orders, some of them armed only with handguns, said they had no choice but to exterminate the animals to protect local residents -- and in some cases, themselves -- as darkness fell.

There had been at least three dozen complaints since 2004 about Thompson's exotic menagerie -- including a giraffe grazing by a highway and a monkey in a tree -- and he had faced more serious charges of animal mistreatment.

Conservationists have for years demanded strict US wildlife ownership laws, especially in Alabama, Idaho, Nevada, North Carolina, Ohio, South Carolina, West Virginia and Wisconsin, where no such laws exist.

"Quite frankly, nobody should have these animals in the first place, so we need to take steps to change laws to make that a reality," Adam Roberts, executive vice president of Born Free USA, told AFP.

"These animals belong in accredited facilities with people who can handle them appropriately."