Microsoft said it had "significant concerns" about reports that the US National Security Agency and its British counterpart, GCHQ, had succeeded in cracking most of the codes that protect the privacy of internet users.
Yahoo said it feared "substantial potential for abuse".
Google said it was not aware of any covert attempts to compromise its systems. However, according to a report in the Washington Post on Saturday, the company said that it had accelerated the encryption of information in its data centers in a bid to prevent snooping by the NSA and the intelligence agencies of other governments.
Documents obtained by whistleblower Edward Snowden and published jointly by the British daily Guardian, the US daily New York Times and the nonprofit news organization ProPublica on Thursday show that agents at GCHQ have been working to undermine encrypted traffic on the "big four" service providers, named as Hotmail (the Microsoft email service now known as Outlook), Google, Yahoo and Facebook.
Yahoo responded with a strongly worded statement on Friday. "We are unaware of and do not participate in such an effort, and if it exists, it offers substantial potential for abuse. Yahoo zealously defends our users' privacy and responds to government requests for data only after considering every applicable objection and in accordance with the law," a spokesman said.
A Microsoft spokesperson said, "We addressed these issues in our blog on July 16. We have significant concerns about the allegations of government activity reported yesterday and will be pressing the government for an explanation."
Tensions between tech firms and US authorities have been escalating. On Monday Microsoft and Google will file their latest legal briefs in a joint attempt to force the Foreign Intelligence Surveillance court to allow them to disclose more information about the requests for confidential information they receive.
The latest reactions come as experts warn the private sector is becoming increasingly distrustful of the NSA and its allies.
Speaking to federal technology website Nextgov.com, Christopher Finan, a former White House and Pentagon official who worked in cyber offence research, said the NSA revelations were undermining relations with the private sector.
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