There had been "remarkable" progress since US-led forces toppled the Islamic regime, but without help the country that once sheltered Osama bin Laden could again pose a international threat, according to the report which ranked Afghanistan 173 out of 178 countries.

Only Burundi, Mali, Burkina Faso, Niger and Sierra Leone in Africa are more impoverished, the United Nations Afghanistan Human Development Index report said.

Afghans' life expectancy is only 44.5 years, at least 20 years lower than neighbouring Central Asian nations.

First-ever assessment of Afghanistan

Officials have never before been able to carry out a proper assessment of Afghanistan's economy, society and education because decades of warfare made it unsafe for them.

The report said there was room for cautious optimism about Afghanistan's future but concluded that "without mincing words, the fragile nation could easily tumble back into chaos".

More effort was needed from both the Afghan government and the outside world or else "Afghanistan will collapse into an insecure state, a threat to its own people as well as to the international community," it said.

Basic human needs must be met

"The basic human needs and the genuine grievances of people — the lack of jobs, health, education, income, dignity and opportunities for participation for the Afghan people — must be met, and international aid must be tightly controlled," it said.

Although Afghanistan's legal economy has grown by 25 to 30 percent since the fall of the Taliban, there has been little trickle-down to the poorest echelons of society, according to the UN.

The report — titled "Security With A Human Face" — found that the poorest 30 percent of the population receive only nine percent of the national income, while the upper third receive 55 percent.

"Our team found the overwhelming majority of people hold a sense of pessimism and fear that reconstruction is bypassing them," said Daud Saba, one the authors of the report.

Half of the population are desperately poor and their poverty is compounded by a lack of social services, poor health, education and nutrition as well as a yawning gap in rights between men and women.

The world's worst education system

Although three million children have gone back to school since the Taliban collapsed, Afghanistan "has the worst education system in the world" and one of the lowest adult literacy rates at only 28.7 percent, the report found.

Most economic activity is fuelled by illicit drugs and Afghanistan is now the world's leading producer of opium, which has underpinned a culture of violence and boosted the strength of private armies.

Violence, torture continue

"Physical violence by armed militias continues, as does torture by security forces, deadly attacks by Taliban, hostage-taking, street gangs and domestic violence against women and children," the report said.

The Taliban continue to launch attacks against US forces, who invaded Afghanistan after the fundamentalist regime refused to hand over bin Laden following the September 11, 2001 attacks.

Years of discrimination and poverty have also relegated Afghan women to a life hemmed in by poverty, malnutrition, exclusion from public life, rape, violence, poor health care, illiteracy, and forced marriage.

Of 300 children surveyed, 72 percent experienced the death of a relative and nearly all witnessed acts of violence.

Only Niger and Burkina Faso ranked below Afghanistan in their treatment of women, the report found.

One woman dies from pregnancy-related causes approximately every 30 minutes, and maternal mortality rates are 60 times higher than in developed countries.

Millions of dollars of foreign aid are flowing into the country but the report warned of the need for measures to limit corruption and ensure the fair flow of aid to prevent an increase in conflict and competition.