A scramble by wealthy states to snap up developing world farmland to ensure their own food security -- especially in Africa  -- could trigger conflict in poorer countries, a UN official said on Wednesday.

World Food Programme deputy executive director Sheila Sisulu told Reuters she would prefer that at least some of the crops produced on land leased to foreign governments stay in the country of origin to contribute to local food security stocks.

"The arable land in Africa is not that plentiful if you consider that desert is growing. Arable land is diminishing because of floods, of droughts. So I fear... conflict," she said on the sidelines of the Non-Aligned Movement summit in Egypt.

"If they grow food, and the food is taken away ... it can be a destabilising issue," she added.

Large swathes of arable but fallow land in Africa have proved attractive investments for rich countries, such as Saudi Arabia, seeking greener pastures to help ensure their own food supplies, especially after sharp price hikes in 2008.

But the land acquisition phenomenon has been labelled exploitative by activists and prompted calls for guidelines.

"It would be better if countries really got good advice on the contractual arrangements that they make. Maybe ... part of the produce must stay to make sure there is food security, rather than just the cash," Sisulu said.

Close to 2.5 million hectares (6.2 million acres) of farmland in five sub-Saharan African countries has been bought or leased since 2004, an investment of $920 million, according to a May report co-authored by international agencies.

Sisulu said the global financial crisis would likely further swell the already growing ranks of the hungry, especially as the downturn bites in poorer countries following drop in worker remittances from abroad.

The United Nations says the number of malnourished people has risen in the past two years and is expected to top 1.02 billion this year, reversing decades of declines. The global recession is expected to make 103 million more go hungry -- a figure Sisulu said may be too low.

"It will grow ... I would say another 50 million, and that is very modest. The additional could easily double (to 100 million) in my estimation," she said. "It wouldn't be in 2009 ... but it will begin to rise from now."    

"It is because the effect of the financial crisis ... is delayed when it comes to the developing countries. There is a lag time, usually about 6 months. So we are at that point now where it will begin to show on the ground," she said.

She said the World Food Programme had collected less than $2 billion of the more than $6.4 billion it estimates is needed this year to meet the urgent hunger needs of 105 million people.

She said that $20 billion in farm aid pledged by G8 leaders last week to help poor nations feed themselves was a welcome development, but cautioned that it might not help all at risk.

"The $20 billion should focus also on alleviating suffering of the vulnerable," she said. "Urban people will not be assisted by agricultural development ... Agricultural development assumes land, capability to work the land. Urban people don't have that." - Reuters