WASHINGTON — President Trump’s abrupt dismissal of the F.B.I. director roiled Washington on Wednesday and deepened the sense of crisis swirling around the White House. Republican leaders came to the president’s defense, and Mr. Trump lashed out at Democrats and other critics, calling them hypocrites.

On Capitol Hill, at least a half-dozen Republicans broke with their leadership to express concern or dismay about the firing of James B. Comey, who was four years into a decade-long appointment as the bureau’s director. Still, they stopped well short of joining Democrats’ call for a special prosecutor to lead the continuing investigation of Russian contacts with Mr. Trump’s aides.

At the White House, Mr. Trump shrugged off accusations of presidential interference in a counterintelligence investigation. He hosted a surreal and awkwardly timed meeting in the Oval Office with Sergey V. Lavrov, the Russian foreign minister, and Sergey I. Kislyak, the Russian ambassador to the United States. Mr. Kislyak’s private meetings with Mr. Trump’s aides are a key part of the sprawling investigation.

White House officials denied American reporters permission to witness the Oval Office meeting or take photographs, but Russian state news outlets published images taken by their official photographer of a beaming Mr. Trump shaking hands with the envoys. The pictures quickly spread on Twitter.