European Council President Donald Tusk speaks with media as he arrives at the EU Summit in Brussels, Belgium, June 28, 2016.  [Photo/Agencies]

European Council President Donald Tusk has warned that lower growth in the UK due to Brexit may lead to a "negative spillover all over the world."

Tusk made the remarks after British Prime Minister David Cameron reported on the outcome of the EU referendum and European leaders discussed the post-Brexit economic situation at the summit of 28 EU countries late Tuesday night.

Without the UK, the remaining leaders of 27 countries join Tusk and other European Union representatives to discuss the future of Europe today in Brussels. This is the first time the UK has been absent from such a meeting since its accession to the block in 1973.

"We also considered the post-Brexit economic situation in the presence of the European Central Bank President, who reassured us about the good and constant cooperation of central banks," said Tusk.

"However, it was also made clear that Brexit means substantially lower growth in the UK, with a possible negative spillover all over the world."

According to Tusk, after Cameron outlined the results of Thursday's referendum, the leaders agreed that an orderly exit was in the interests of everyone involved, especially the UK.

"Leaders understand that some time is now needed to allow the dust to settle in the UK. But they also expect the intentions of the UK government to be specified as soon as possible," said Tusk.

"This was a very clear message which I believe Prime Minister Cameron will take back to London."