The UN children's agency says child mortality is decreasing, but the rate of decline is not enough.

联合儿童署称儿童死亡率在下降，但是下降率仍不够。

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Unicef says preventable diseases are the biggest killers of children

A new report says more than eight million children under five died last year with pneumonia²（肺炎） and diarrhoea（腹泻） the two leading causes of death.

Unicef says 40% of under-five deaths take place in just three countries - Nigeria, India and DR Congo.

The report singled out Malawi and Eritrea as success stories, but said in South Africa child mortality had risen.

Unicef says the world is failing to reach the UN's target of a two-thirds reduction in under-five child mortality between 1990 and 2015.

In 1990, 12.5 million children under the age of five died.

"Compared to 1990, 10,000 fewer children are dying every day," said Unicef Executive Director Ann Veneman in a statement.

"While progress is being made, it is unacceptable that each year 8.8 million children die before their fifth birthday."

'Improvement possible'

Unicef says the tools are there to significantly reduce child mortality.

They include bed nets to stop malaria³（疟疾）, improved water and sanitation⁴（环境卫生） and increased vaccination⁵ programmes.

Those countries that use these tools - even some of the poorest nations - have seen big improvements in child survival rates, Unicef says.

But in some countries progress is at best slow and at worst non-existent.

In South Africa, under-five mortality has actually increased since 1990.

The reason, Unicef says, is the high rate of HIV and Aids among mothers.