UNICEF and the U.N. World Food Program estimated in a report that 48.6 percent of the country's 20 million children aged 6 months to 5 years are chronically malnourished, a devastating problem caused by food shortages and high prices.

The report said that although the country has systems in place to help impoverished people, they "should be expanded and better targeted toward areas where malnutrition and household food insecurity are most prevalent."

Carel de Rooy, a UNICEF representative in Dhaka, called for urgent action to improve the situation, which he called "a silent emergency."

Chronic malnutrition hampers growth and can necessitate medical care to stave off bone and muscle loss, organ failure and possible death.

The U.N. groups assessed the impact of increasing food prices in 2008, surveying 4,175 children across the country during the November to January harvest season. The country has one of the highest levels of child malnutrition in South Asia, the report said.

De Rooy warned that Bangladesh might miss its chance to meet the U.N. Millennium Development Goals, which call for cutting extreme poverty in half by 2015. The World Bank and the U.N. had earlier lauded Bangladesh's efforts to achieve the goals.

The country's economy has grown by about 6 percent a year in recent years, helping to reduce the percentage of people living on less than $1 a day to 40 percent from 49 percent in 2000, the World Bank says. But one in four households still cannot obtain adequate food, the U.N. report said.

In November, the World Bank said food prices in Bangladesh had risen more than 20 percent, eroding some of the gains from the economic growth and slowing the pace of efforts to reduce poverty.

Food production last year was devastated by Cyclone Sidr, which hit in 2007 as the country struggled to recover from monsoon floods.

Food prices in Bangladesh have been relatively stable over the past two months, but some officials say the food crisis still poses a major threat.

"Even if the prices of food are now falling, the crisis is far from being over," John Aylieff, the WFP chief in Bangladesh, told a news conference Sunday.

Bangladesh's new government headed by Prime Minister Sheikh Hasina has promised to keep food costs stable and is considering lowering the prices of rice and other basic foods.

Bangladesh, a nation of 150 million people, is plagued by natural disasters such as floods and cyclones, as well as poor infrastructure and corrupt governance.