A breach of telecoms companies that the United States said was linked to China was the "worst telecom hack in our nation's history - by far", the chairman of the Senate Intelligence Committee told the Washington Post on Thursday.

Earlier this month, U.S. authorities said China-linked hackers had intercepted surveillance data intended for American law enforcement agencies after breaking into an unspecified number of telecom companies. The hackers compromised the networks of "multiple telecommunications companies" and stole U.S. customer call records and communications from "a limited number of individuals who are primarily involved in government or political activity," according to a joint statement released by the FBI and the U.S. cyber watchdog agency CISA on Nov. 13.