High winds over Greece have left dead thousands of swallows and swifts migrating from Africa to Europe, bird watchers said Thursday.

The birds have been found in the streets of Athens, on apartment balconies in the capital, in the north, on Aegean islands and around a lake close to the seaport of Nauplia in the Peloponnese.

"It's a major disaster," Maria Ganoti of the wildlife protection group Anima told AFP. "Over the last three days because of high winds in the north and over the Aegean Sea, thousands of small birds have been found dead or gravely injured," she said.

The Greek ornithologist association said "the night of April 5-6 was disastrous for migrating birds due to strong winds, low temperatures and rain in some regions.

"Southerly winds pushed flocks of birds from north Africa into air currents from the north of the Aegean sea and particularly the islands. "To escape, exhausted birds, mainly swallows and swifts, which catch flying insects for food, headed for the Greek mainland," the association said in a statement.

It urged people "to take care in the street where exhausted birds often land after covering thousands of kilometres (miles)".

Greece, in southeast Europe, is on the flight path for hundreds of thousands of birds which migrate north in spring and south in autumn.