Retail prices of chicken and eggs in Japan in June rose to their highest levels since the agriculture ministry started collecting data in August 2003.

The national average price of chicken rose ?1 per 100 grams from the previous month to ?155 per 100 grams, the ministry said on Tuesday.

Demand for relatively inexpensive chicken has been solid amid soaring prices. Higher prices of imported chicken helped lift demand for domestic products, pushing up overall chicken prices, the ministry said.

The national average price of a packet of 10 eggs stood at ?309, matching the highest level marked in March and May. The increase has been attributed to a cull of chickens due to bird flu outbreaks.

The agriculture ministry announced a package of measures to ensure a stable supply of eggs, whose prices often soar due to bird flu outbreaks. The measures include promoting chicken management methods to minimize culling and establishing a public-private study group on ways to detect infected chickens early.

The ministry¡¯s monthly survey covers 470 stores across the country to calculate the average price. The latest survey was conducted from June 8 to 10.