BRUSSELS (AFP) - European Commission head Jean-Claude Juncker on Friday told the EU's British employees that their jobs were safe for now even after the historic decision by UK voters to exit the bloc.

"I know that many of you are concerned about your future after this vote," Juncker said in a letter to Commission staff seen by AFP.

But he said employees at the Commission, the EU's executive arm, above all "work for Europe".

"You left your national 'hats' at the door when you joined this institution and that door is not closing on you now," Juncker said, without outright guaranteeing job safety for the future.

The commission employs 1,164 British citizens, about 3.5 per cent of the vast bureaucracy's 33,000 total, according to EU data.

"I know you all have legitimate expectations about your rights and duties, your families who might have followed you to Brussels and your children who might be enrolled in schools here," the letter said.

"Let me assure you that I will do everything in my power as President of the Commission, to support and help you in this difficult process," Juncker said.