"There's something going on and it's not good," Trump said. | Isaac Brekken/Getty Images Donald Trump: Brussels is ‘like a hellhole’ US Republican presidential candidate defended his proposed Muslim ban.

U.S. Republican presidential candidate Donald Trump said that living in Brussels is like living in “a hellhole” because of the lack of "assimilation" of the Muslim population.

"You go to Brussels — I was in Brussels a long time ago, 20 years ago, so beautiful, everything is so beautiful — it's like living in a hellhole right now,” he said in a TV interview with FOX Business Network.

Trump was asked about his proposal to ban Muslim migrants and tourists to the U.S., which he suggested last month.

“There is something going on Maria," he told FOX's Maria Bartiromo. "Go to Brussels, go to Paris... There's something going on and it's not good. Where they want sharia law... there has to be some assimilation.”

"We have a president who doesn't want to even talk about radical Islamic terror," he added.

Trump has been widely criticised for the proposal, which he said was needed to keep the U.S. safe from terrorism.