German Chancellor Angela Merkel says she expects Great Britain to leave the European Union after a majority there voted leave, even though an online petition calling for a second referendum attracted more than 4 million signatures.

The validity of some of the signatures has been questioned.

Merkel said in her annual summer interview to public broadcaster ZDF on Sunday that "I'm dealing with the realities and I very strongly believe that this application (to leave the EU) will be made."

The chancellor also vowed to continue working against illegal migration and human trafficking that tolerates the drowning of thousands of migrants in the Mediterranean.

She said "we cannot expect people to come here under unspeakable circumstances and that hundreds, even thousands lose their lives in the Mediterranean."