Retail prices of domestic and imported beef continued rising to new records last week amid the import ban on U.S. beef, the Agriculture, Forestry and Fisheries Ministry said Monday.

The average price of imported frozen beef rose to 364 yen per 100 grams in the Jan. 26-30 period, up 1.9 percent, or 7 yen, from the previous week, while the retail price of domestic beef rose 0.6 percent, or 4 yen, to 670 yen per 100 grams.

Both are the highest levels since the ministry began tracking weekly meat prices last August.

Pork prices dropped 0.8 percent, or 2 yen, to 235 yen per 100 grams on average after rising for weeks as demand increased after the government imposed the beef import ban in late December.

Chicken prices leveled off at 117 yen per 100 grams, with little influence felt on the market from the suspension of poultry meat imports triggered by the outbreak of bird flu across Asia, as well as the late December outbreak of the disease on a farm in Yamaguchi Prefecture.

Nakau out of 'gyudon'

Nakau Co., a nationwide chain that specializes in "gyudon" beef on rice dishes, stopped serving the dish Monday afternoon at almost all of its outlets.

The chain ran out due to Japan's ban on beef imports from the United States. Nakau is the first major gyudon chain to run out of stock.

At a Nakau restaurant in Yodogawa Ward, Osaka, many customers were ordering gyudon knowing that Monday would be the last day unless U.S. beef imports are resumed.

"We feel sorry for our customers who liked our gyudon, but hopefully this will be an opportunity for them to try our other products" such as chicken and pork dishes, said Yoko Murakami, manager of the restaurant.

Yoshinoya D&C Co. -- the nation's biggest gyudon chain, with nearly 1,000 outlets -- expects to run out in mid-February.

The chains are introducing alternatives such as pork curry or salmon eggs with rice.