Kenya's horticulture industry has lost $12 million to the volcano-induced European airspace closure and it will take several weeks to recover even if flights resume now, its association of exporters said on Monday.

Horticultural exports are the leading hard currency earner in east Africa's largest economy, raking in 71,6 billion Kenya shillings ($924 million) last year. The sector provides thousands of jobs in a country with a high unemployment rate.

"It is bad. We have lost $3 million a night so that is a total of about $12 million as of last night," Stephen Mbithi, the head of the Fresh Producers Exporters Association of Kenya told Reuters by phone.

FPEAK is an umbrella body that brings together 150 firms including growers of vegetables, flowers and fruit. Some 82% of total output is exported to the European Union.

Mbithi said the country flies out 1000 tones of fruit and vegetables every night at this time of the year and only about 100 tonnes left on Monday morning, destined for Spain.

"We want to see if we can open a corridor into Spain then we can send everything from Spain straight to Germany, Netherlands Belgium and everywhere we sell," he said.

He said more workers would be asked to stay away from farms after 5000 employees, mainly harvesters, stopped working over the weekend when refrigerated stores reached capacity.

"The stores are full, there is no more space to keep anything, we are looking to suspend more work today ... we are only stopping harvesting workers," he said.

Foreign exchange traders said the Kenyan shilling was likely to remain under pressure against the dollar as the flight ban was bound to hit hard currency inflows.