Egypt started seizing and slaughtering herds of pigs on Thursday as a precaution against swine flu, officials and farmers said, despite resistance by farmers and criticism from the UN.

Egypt, already hit hard by bird flu, fears another flu virus could spread quickly in a country where most of the roughly 80 million population live in the densely packed Nile Valley, many in crowded slums around Cairo.

But the United Nations said the mass cull of up to 400,000 pigs was 'a real mistake' because the new strain -- a mix of swine, avian and human viruses -- has not been found in pigs.

Farmers in the most populous Arab country said the state had begun confiscating animals. State news agency Mena said Egypt had also culled thousands of birds as a precaution.

'They have destroyed us. The pigs were our livelihood,' said 21-year-old Hanan Ahmed, whose family runs a small farm with around 25 pigs in Cairo.

'They took them. They kidnapped them. And they beat them and us. They said they will take them to the slaughterhouse and kill them there,' she added, saying she had received no compensation.

The H1N1 swine flu virus is spread by people, not pigs. But culling swine, largely viewed as unclean in Muslim Egypt, could help quell any public panic.

Pigs are mainly raised by the country's Christian minority.

Dozens of pigs were killed in the early phase of the cull. In the southern village of Deir Abu Hennes, workers suffocated 25 piglets in plastic sacks and killed dozens of adult pigs and gave the meat to their owners, a local official said.

Some farmers there took their pigs to a graveyard to try to hide them from authorities, but the animals were found and killed on the spot, the official and residents said.

Swine flu has killed up to 176 people in Mexico and one in the United States, and cases have also been reported in Peru, Canada, Europe, Israel and New Zealand. Egypt has not reported any cases, but has stepped up monitoring at airports.

Agriculture Minister Amin Abaza said authorities had already confiscated more than 1,000 pigs despite efforts by some farmers to hide the animals. He said the pigs would be slaughtered and their meat would be frozen.

Abaza said he was seeking the army's help with the slaughter, which Egyptian state media reported could take up to a month to complete.

In one slaughterhouse near Cairo, workers wearing masks used their boot-clad feet to hold down the snouts of pigs while they tested them for illness prior to slaughter.

'The issue of slaughtering more than 300,000 heads of pig is a difficult one, especially since private pig slaughterhouses are not enough. We will seek the help of armed forces slaughterhouses,' Abaza told Reuters.

'The meat will be preserved in freezers after it is removed from the bones and will be offered for sale to consumers,' he said.

Egyptian officials have stressed that while they believed there was a need for a cull, the meat was safe.

An official from the UN Food and Agriculture Organisation said on Wednesday his group had been trying unsuccessfully to reach Egyptian officials to correct any confusion about the virus.

The Paris-based Organisation for Animal Health said states should focus efforts on 'appropriate disease surveillance' and strengthening biosecurity measures at premises where pigs are handled and slaughtered, rather than culling them.

'The culling of pigs will not help to guard against public or animal health risks presented by this novel A/H1N1 influenza virus and such action is inappropriate,' the organisation said in a statement.

Egypt's state-run Al-Ahram newspaper has said pig owners could receive 1,000 Egyptian pounds ($177) per animal in compensation, but an independent newspaper reported on Thursday no compensation would be paid.<