WINDHOEK, July 18 (Reuters) - Namibia, sub-Saharan Africa's driest country, is suffering its worst drought in a generation, with more than 100,000 children at risk of malnutrition, the United Nations said on Thursday.
President Hifkepunye Pohamba declared a national emergency in the sparsely populated southern African nation after the failure of crops in May, and earmarked $20 million of relief for the worst-hit households.
Many farmers are now being forced to sell cattle for which there is no grazing, while cow-herds from Angola are reported to have crossed the border in search of food, fuelling tribal tensions as competition for scarce pastures intensifies.
"The shortages of food and water are increasing the immediate threat of disease and malnutrition," said Micaela Marques De Sousa, the Namibia representative of UNICEF, the U.N.'s children's agency.
"But anecdotal reports already indicate children are dropping out of school, a clear sign of stress and vulnerability in families."
Namibia, which won independence from neighbouring South Africa in 1990, classifies as a middle-income country although a quarter of its 2 million people live in poverty.
While agriculture accounts for 5 percent of the economy, a third of Namibians are dependent on some form of subsistence farming.
(Reporting by Servaas van den Bosch; Editing by Ed Cropley)