Yahoo said Tuesday it received between 12,000 and 13,000 requests for user data from U.S. law enforcement agencies over the last six months.
The Web portal company followed other major tech companies in revealing the extent of its involvement in the government's web surveillance program. Its report indicates it has had more requests than Facebook(FB), Microsoft (MSFT)or Apple(AAPL).
As with other companies reporting data requests, Yahoo said most of the orders concerned criminal investigations.
In a blog post headlined "Our Commitment to Our Users' Privacy," CEO Marissa Mayer and Yahoo(YHOO) general counsel Ron Bell said they were prevented from breaking out the numbers of Foreign Intelligence Surveillance Act requests because they are classified.
"We strongly urge the federal government to reconsider its stance on this issue," they wrote.
Tech and telecom companies have been under pressure to clarify their involvement in cyber-snooping since American computer analyst Edward Snowden leaked details of the government system for monitoring millions of e-mails, photos, search histories and other data earlier this month.
Snowden's leaks have sparked a furious debate about the scale and scope of the National Security Agency surveillance program -- known as Prism -- which dates back to the days after the 2001 al Qaeda attacks on New York and Washington.
Apple said Monday it had received as many as 5,000 requests covering up to 10,000 user accounts since December 2012.
Facebook received between 9,000 and 10,000 requests in the last half of 2012, targeting between 18,000 and 19,000 accounts. Over the same period, Microsoft received between 6,000 and 7,000 criminal and security warrants, subpoenas and orders affecting as many as 32,000 customer accounts.
Prism: What the NSA could know about you
Yahoo said it would publish a global law enforcement transparency report later this summer covering the first half of 2013. That report will be updated twice a year.
"We will continually evaluate whether further actions can be taken to protect the privacy of our users and our ability to defend it," it said.
A series of blog posts on Monday purportedly by Snowden said he leaked classified details about U.S. surveillance programs because President Obama worsened "abusive" practices instead of curtailing them as he promised as a candidate.
In 90 minutes of live online chatting, the person identified as Snowden by Britain's Guardian newspaper and website insisted that U.S. authorities have access to phone calls, e-mails and other communications far beyond constitutional bounds.