Photo: CFP

Every time Ai Yuanxi (alias) turns on TV, the first pictures she sees are those from her son. He lives in Berlin and sends pictures of her 16-month-old grandson to her TV every day.

In a Reuters exclusive report published on Tuesday, sources familiar with the matter told the British media that the US company has searched hundreds of millions of customers' email accounts since last April at the request of the National Security Agency (NSA) or Federal Bureau of Investigation (FBI).

Citing two unnamed former employees, it reported that the company's decision to obey the order prompted at least two officials, including then-chief information security officer Alex Stamos, to leave last year over ethical issues concerning the program.

It was likely to be the first known case that a US company agreed to an intelligence agency's order by searching all incoming messages, but it was unclear what information the intelligence agencies were looking for and also what data Yahoo may have handed over, it reported.

"Yahoo is a law-abiding company, and complies with the laws of the United States," the company said in a statement, declining any further comment.

The Office of the Director of National Intelligence did not respond to a request for comment.

According to US laws, the country's intelligence agencies have the right to order phone and Internet companies to provide customer data when they believe there are possible connections with terror actions.

It was not known whether other US email providers received similar requests from the intelligence community.

Google, which runs Gmail, said in a statement that the company never received such a request. "But if we did, our response would be simple: 'no way,'" it said.

Microsoft said they "have never engaged in the secret scanning of email traffic like what has been reported today about Yahoo."

US authorities have frequently come under fire for violations of citizens' right of privacy in the name of social security. Patrick Toomey, an attorney with the American Civil Liberties Union, called the order "unprecedented and unconstitutional."

"It is deeply disappointing that Yahoo declined to challenge this sweeping surveillance order, because customers are counting on technology companies to stand up to novel spying demands in court," he said in a statement.