All restaurants, fast food shops, catering services, schools, hospitals and government agencies serving beef will have to inform consumers whether the meat is from the United States, a measure officials hope will ease public fears over mad cow disease, the South Korean news agency Yonhap reported Sunday.

It said the new directive had been issued by the government's Ministry of Food, Agriculture, Forestry and Fisheries, and was set to take effect beginning this week. It will apply to 640,000 restaurants, and non-compliance will produce a $4,800 fine, Yonhap said.

The move comes a day after 50,000 protesters flocked into the streets of Seoul, the biggest rally yet in a series of ongoing vigils and demonstrations denouncing the government's decision to allowed long-banned U.S. beef imports back into the country.