Sunday's call came from Rural Development Minister Ahmedou Ould Ahmedou and Economic Development Minister Abdellahi Ould Cheikh Sidya who summoned ambassadors from donor countries, the European Union, and the representative of the   United Nations Food and Agriculture Organisation. 

Swarms of locusts from north Africa have been heading in huge numbers for countries to the south, among them Chad, Mali, Mauritania, Niger and Senegal. 

The ministers said the situation was serious and everyone had to help if a lasting catastrophe was not to ensue. 

Mauritania has submitted a plan to treat 300,000 hectares (1158 sq miles) at a total cost of $5.6m (4.5 million euros), but Ould Ahmedou said this was a conservative estimate that could be overtaken by the sheer size of the invasion. 

A gloomier estimate would require 500,000 to 800,000 hectares (1930 to 3088 sq miles) to be treated, according to the minister who said: "The serious situation requires the mobilisation of all our partners." 

He said seven regions devoted to crops and grazing were being invaded, with a threat to farm production and animal husbandry and "a further complication in the fight against poverty which is being fought throughout the country on all fronts." 

The rural sector produces 20% of the gross national product and accounts for 60% of jobs, he said. 

Since October 2003 more than 300,000 hectares had been treated due to government efforts, he said.