Ethiopia is facing a huge wave of refugees from South Sudan, where the spectre of famine threatens to heap further misery on a people already rocked by civil war, the UN's food aid agency warned on Wednesday.
"The numbers are increasing exponentially in a very short period of time," said Abdou Dieng, head of the World Food Programme's Ethiopia operations.
There are already around 147,000 South Sudanese refugees in camps in neighbouring Ethiopia, and at least 1,500 more are crossing the border every week.
"The situation is not improving in South Sudan, so we expect that they will continue to come. If there is a famine in South Sudan, as many people think there will be, that will push more people to come into Ethiopia," he told reporters.
The UN forecasts the South Sudanese refugee numbers could spiral to 300,000 by the end of the year. All told there are around half a million refugees -- largely women and children -- in camps in the country.
Apart from the South Sudanese, most are from Somalia, which huge numbers fled amid conflict and a 2011 drought, and Eritrea, where mounting numbers are escaping the iron grip of the country's regime.
"The government has a policy that they call the 'open-door policy' for refugees. Ethiopia today is hosting one of the biggest refugee numbers, without talking too much about it," said Dieng.
The UN needs around $20 million (14.6 million euros) per month to help feed refugees in Ethiopia, but is facing a massive funding shortfall and fears that its coffers will be empty by October, he added.
South Sudan only gained its independence from Sudan three years ago after decades of fighting, and has been ravaged by ethnically-tinged conflict between rebels and the government since December.
The fighting has driven more than one million people from their homes, meaning that many farmers have missed the planting season.