He got support from the chairman of the Senate Intelligence Committee, Richard M. Burr of North Carolina, a Republican leading what appears to be the most active congressional investigation on Russia.

“I am troubled by the timing and reasoning of Jim Comey’s termination,” Mr. Burr said in a statement. It “further confuses an already difficult investigation by our committee,” he said, adding that Mr. Comey had been “more forthcoming with information” than any of his predecessors.

The Democratic vice chairman of the Senate panel, Mark Warner of Virginia, said in a brief interview that Mr. Comey’s firing “means the Senate Intelligence investigation has to redouble its efforts, has to speed up its timeline, because we’ve got real questions about the rule of law.”

Even before Mr. Comey was fired, the committee was pressing forward with its investigation. Late last month, it asked a number of high-profile Trump campaign associates to hand over emails and other records of dealings with Russians. Mr. Warner said the committee planned to announce on Wednesday who had complied and who had not.