London (AFP) - US presidential hopeful Donald Trump on Wednesday said Muslims were "absolutely not reporting" suspected attackers in an interview with British television following the Brussels attacks.

"I would say this to the Muslims, and in the United States also, when they see trouble they have to report it," Trump told ITV television, a day after triple blasts killed some 30 people at Brussels airport and on the city's metro system.

"They're not reporting it, they're absolutely not reporting it and that's a big problem," said Trump, who is the favourite to win the Republican nomination for the US presidential election on November 8.

"It's like they are protecting each other but they are really doing very bad damage... They have to open up to society, they have to report the bad ones," he told interviewer Piers Morgan.

Trump's comments were immediately rejected by the Muslim Council of Britain (MCB), which represents hundreds of mosques and charities, and by one of Britain's top counter-terrorism officers, Neil Basu.

"He is wrong," Basu, a deputy assistant commissioner at London's Metropolitan Police, told BBC Radio.

"If we demonise one section of the community that is the worst thing we can do. We are absolutely playing into the terrorists' hands of making people feel hate," he said.

Miqdaad Versi, the MCB's assistant secretary-general, said Trump's comments "fuel this idea of bigotry".

They "really fuel the thing that terrorists themselves want -- that Muslims are apart from the West and cannot be seen as equal citizens," he said.

Trump has drawn controversy before by calling for Muslims to be barred from entering the United States following a deadly shooting attack in San Bernardino, California in December.