SEOUL (Reuters) - South Korea on Monday (Dec 26) mobilised armed forces to play an active part in its biggest-ever poultry cull as the spread of a highly contagious strain bird flu continued, ordering that another 1.6 million birds be destroyed in affected areas within 24 hours.

The latest cull, announced in a statement by the Ministry of Agriculture, Food and Rural Affairs, brings the total number of birds to be destroyed to 26 million in an outbreak first confirmed on Nov 18.

Quarantine and sanitary restrictions were implemented after the initial cases but the flu has spread.

Having previously stood guard at facilities affected by the outbreak, Korea's military will now actively help destroy birds and disinfect farms to accelerate the cull, the ministry said. Culls announced previously took two to three days to complete because of a lack of manpower, it said.

The rapid spread of the H5N6 strain of the virus has caused Seoul to raise its bird flu alert to the highest level possible for the first time. The army's mobilisation comes amid fears of a regional epidemic across Northeast Asia, with Japan and China also battling to curb the spread of bird flu.

More than 78 per cent of South Korea's culled birds are egg-laying hens, according to the ministry statement. With egg supplies tightening, the ministry said it would temporarily lift tariffs for imported eggs, and also finance some shipping fees to ease the shortage.

South Korea has yet to detect any human infection since Nov 18, unlike China. Last week, China confirmed its first two human deaths this winter, from the H7N9 bird flu strain.

The last major bird flu outbreak in mainland China occurred from late 2013 to early 2014, killing 36 people with more than US$6 billion in losses for the agricultural sector.