The case is being closely watched by large and small technology firms that include Intel, IBM and General Electric, as well as the U.S. government, some of whom have filed briefs supporting or rejecting the claims of the companies involved in the suit before the court on Tuesday.

At issue is what constitutes an obvious invention and what kinds of innovations are eligible for a patent. A previous court ruling made it possible for combinations of existing technologies to be patented, paving the way for what some companies see as nuisance lawsuits.

Intel Corp., the world's largest computer chip-maker, and semiconductor maker Micron Technology, Inc., jointly filed a brief with the court supporting KSR's argument that combinations of previous inventions should be ineligible for a patent.

To promote innovation, "patents must be restricted to those claims that truly advance the body of relevant knowledge," Intel and Micron say in the their filing. "Claims encompassing simple combinations of the prior art that would have been apparent to anyone trained in the relevant field do not reflect innovation and do not warrant patent protection."

The companies argue that the court should strike down the section of the law that allows combinations of existing technology to be patented and set a higher standard.

The U.S. government has also weighed in on the matter, filing a brief supporting the Canadian company's position.

Park Kyung-hee, an official at Iksan city hall, said Wednesday 426 pigs and four dogs have been killed along with 127,200 chickens and 6.8 million eggs.

Park said nearly 700 dogs -- bred on farms for consumption -- were to be killed, but it was unclear when the slaughter would take place. She said efforts are focused on destroying more susceptible animals like poultry and pigs for now.

A village resident, Im Soon-duck, said she was more concerned about losing her three pigs than a dog, which was a present from her daughter in Seoul. Im lives next to a chicken farm where a second outbreak of bird flu was confirmed Tuesday, about 250 kilometers (155 miles) south of Seoul.

"Dogs are good for keeping us not bored. But pigs -- it costs us a lot to buy those pigs," said the 66-year-old Im. "We people in rural areas depend on pigs and cows for our living."

The government is to compensate farmers for their lost livestock, but the exact amount is not known.

Since ravaging Asia's poultry in late 2003, the H5N1 virus has killed at least 153 people worldwide. Infections among people have been traced to contact with infected birds, but experts fear the virus could mutate into a form that could create a human pandemic.

Dogs bred for food are regularly slaughtered in South Korea, where dog meat is widely consumed, especially among middle-aged men who believe bosintang, or dog soup, is good for stamina and virility.

"I do feel bad that my dogs would have to be killed when they are not even sick," said Noh Jung-dae, a 63-year-old farmer who also lives next to the chicken farm that saw the latest outbreak. "But, if the government has to do it to prevent the disease, what can I do?"

Noh said he had planned to eat some of the six dogs that he was raising.

The scene in the rural area is quite different from the expensive neighborhoods of Seoul. In the capital an increasing number of people keep cats and dogs as pets. Pet shops are easy to find in the city, where there are even coffee shops specially designed for pets and their owners.

In Iksan, some younger villagers raised concerns about the slaughter.

"It's just too cruel to indiscriminately kill other livestock when there is obviously no proof these animals can transmit the bird flu virus to humans," said 29-year-old Kim Sung-tae. "I have little puppies that are as small as my palm. How can they have the heart to kill those small things?"

Animal-rights activists called the government move "unacceptable."

"The government should know better about their course of action," said Kum Sun-lan, spokesman for Korea Animal Protection Society. "It is unacceptable how they just move on with the extermination procedure without any reliable evidence for it."

Park said the killing of all animals was in accordance with national guidelines, adding that stray cats and mice will also be killed.