Bird flu has led to a record 12.3 million chickens being culled in Japan since October.

The country's agriculture ministry says that despite the spread of the disease, there are enough eggs for home use. But it is warning that egg supplies for food processing may be affected.

Seventy farms across 25 prefectures have been affected by bird flu so far this season.

Producers tend to prioritize the supply of eggs to retailers for home use because they command higher prices.

The ministry says that has resulted in cases where the supply of eggs to food manufacturers has been disrupted.

Leading convenience store chain, Seven-Eleven Japan, says it stopped selling about 15 of its egg products nationwide on Tuesday.

The company also says it has reduced the amount of boiled egg used in about 10 products including salads and sandwiches. It has increased the proportion of ham and vegetables instead.