RIO DE JANEIRO — Thousands of protesters fanned out on the streets of Brazilian cities on Sunday to voice indignation with political leaders who are trying to stymie anticorruption investigations.

The protesters focused much of their ire on the politicians at the helm of Brazil’s scandal-ridden Congress, including Rodrigo Maia, the speaker of the lower house, and Renan Calheiros, the powerful head of the Senate, after lawmakers gutted an anticorruption bill last week.

That move touched a nerve among many people in the country as Brazil mourned the victims of the crash of the plane carrying the Chapecoense soccer team last Monday. In a marathon session, the lower house rewrote the legislation to curb the power of prosecutors and judges guiding graft inquiries.

The administration of President Michel Temer, who took office just six months ago after a bitter fight to impeach his predecessor, Dilma Rousseff, is showing signs of vulnerability over corruption scandals in its ranks and its inability to mend an ailing economy.