Brazil's president is dismissing protests against his cuts to education funding, saying the student demonstrators are "useful idiots" who have "nothing in their heads".

President Jair Bolsonaro spoke from Dallas, Texas, even as large crowds gathered in several Brazilian cities to denounce cuts that include a 30% reduction for the discretionary budget of federal universities. Scholarships for masters and doctoral students are also being suspended.

In Brasilia, thousands of protesters carried banners down the vast Esplanade of Ministers past the lower house of congress, where the education minister had been summoned to testify about the budget cuts

Federal education officials say the $1.85 billion reduction for public education is part of a wider government effort to slash spending.