The number of young children who die each day has plunged over the past two decades, new United Nations figures show, but the world is still lagging far behind in efforts to achieve its target for reducing child mortality.

The latest estimates, issued by the UN Children's Fund (UNICEF) and the UN World Health Organization (WHO), indicate that the number of children under the age of five who perish each year fell from more than 12 million in 1990 to about 7.6 million last year.

That decrease means about 12,000 fewer children are dying each day than they were two decades earlier.

Greater access to health care, particularly in remote areas, broader immunization coverage and higher-quality care in many countries are among the factors being cited for the improvement.

Child mortality rates are dropping in every region of the world, including the area with the highest number of under-five fatalities, sub-Saharan Africa, where the rate of the decline has even accelerated in recent years.

Success stories include Niger, Malawi, Liberia, Timor-Leste, Sierra Leone, Nepal and Bangladesh, all of which have experienced substantial falls in child mortality rates since 1990.

UNICEF Executive Director Anthony Lake said the new figures showed that "we can make progress even in the poorest places, but we cannot for a moment forget the chilling fact of around 21,000 children dying every day from preventable causes.

"Focusing greater investment on the most disadvantaged communities will help us save more children's lives, more quickly and more cost effectively," he added.

In the past two decades the under-five mortality rate dropped by more than a third – from 88 deaths per every 1,000 live births to 57 deaths.

Yet that is well short of the Millennium Development Goal (MDG), agreed to by world leaders at a UN summit in 2000, for child mortality rates to fall by two thirds by 2015.

Margaret Chan, Director-General of WHO, called for increased investment in children's health in the years ahead, as well as greater efforts to boost nutrition, immunization coverage, water and sanitation.

Ian Pett, UNICEF's chief of health systems and strategic planning, told the UN News Centre that a combination of factors – such as integrated immunization schemes that ensured children received multiple vaccinations – rather than any one single factor had led to the steep improvement.

He said many countries had taken different paths to record similar improvements: Sierra Leone, for example, recently cut user fees for child health and maternal health, while Nepal had focused on innovative solutions using village women as volunteer health-care workers in remote areas.

Neonatal sepsis, pneumonia, diarrhoea and malaria remain the biggest killers, although death rates from malaria have fallen in recent years.

Tessa Wardlaw, the chief of the agency's statistics and monitoring section, noted that about half of all deaths last year of children under the age of five occurred in just five countries: India, Nigeria, the Democratic Republic of the Congo (DRC), Pakistan and China.

Thursday's estimates have been prepared by a UN inter-agency group that comprises UNICEF, the WHO, the World Bank and the UN Population Division.