(Adds letter from Blumenthal and Rubio)
WASHINGTON, Oct 9 (Reuters) - The top Republican on the Senate Commerce Committee has asked Apple Inc, Amazon.com Inc and Super Micro Computer Inc for staff briefings about a Bloomberg report that the Chinese government implanted malicious hardware into server motherboards provided by Super Micro.
Senator John Thune said in letters to the chief executives made public on Tuesday that he had sought staff briefings by Oct. 12 from the three companies.
"Allegations that the U.S. hardware supply chain has been purposely tampered with by a foreign power must be taken seriously," Thune wrote.
The companies did not immediately comment on Tuesday on Thune's letter. All have denied the report, published by Bloomberg Businessweek on Thursday.
Separately, Republican Senator Marco Rubio and Democratic Senator Richard Blumenthal wrote to Super Micro's chief executive, Charles Liang, and asked him to provide by Oct. 17 information including when the company first became aware of the report and whether and how it investigated.
"If this news report is accurate, the potential infiltration of Chinese backdoors could provide a foothold for adversaries and competitors to engage in commercial espionage and launch destructive cyber attacks," the senators said in their letter, which was seen by Reuters.
Apple's top security officer, George Stathakopoulos, told Thune and other members of Congress in a letter on Sunday that the company had found no sign of suspicious transmissions or other evidence that it had been penetrated in a sophisticated attack on its supply chain.
Stathakopoulos said he would be available for briefings this week. (Reporting by David Shepardson and Patricia Zengerle; Editing by Bill Rigby and Darren Schuettler)