At least half the world's population is unable to access essential health services and many others are forced into extreme poverty by having to pay for healthcare they cannot afford, the World Health Organization said on Wednesday.

Some 800 million people worldwide spend at least 10 percent of their household income on healthcare for themselves or a sick child, and as many as 100 million of those are left with less than $1.90 a day to live on as a result, the WHO said.

In a joint report with the World Bank, the United Nations health agency said it was completely unacceptable that more than half the world's people still don't get the most basic healthcare.

"If we are serious - not just about better health outcomes but also about ending poverty - we must urgently scale up our efforts on universal health coverage," World Bank President Jim Yong Kim said in a statement with the report.

The report had some good news: This century has seen a rise in the number of people getting services such as vaccinations, HIV/AIDS drugs, and mosquito-repelling bednets and contraception, it said.

But there are wide gaps in the availability of services in sub-Saharan Africa and southern Asia, the report found. In other regions, basic services such as family planning and child immunisation are more available, but families are suffering financially to pay for them.

Yong Kim said this was a sign that "the system is broken".

"We need a fundamental shift in the way we mobilise resources for health and human capital, especially at the country level," he said.