DHAKA: US authorities threatened to fine Yahoo $250,000 a day if it failed to comply with a secret surveillance program requiring it to hand over user data in the name of national security, court documents showed Thursday.

The documents, made public in a rare unsealing by a secretive court panel, "underscore how we had to fight every step of the way to challenge the US government's surveillance efforts," Yahoo general counsel Ron Bell said in a blog post, reports the Yahoo News.

The documents shed new light on the PRISM program revealed in leaked files from former National Security Agency contractor Edward Snowden.

The program allowed US intelligence services to sweep up massive amounts of data from major Internet firms including Yahoo and Google.

Bell said 1,500 pages of documents were ordered released by the Foreign Intelligence Surveillance Court in the case dating from 2007. He said that in 2007, the government "amended a key law to demand user information from online services."

"We refused to comply with what we viewed as unconstitutional and overbroad surveillance and challenged the US government's authority," he said.

Yahoo's court challenge failed and it was forced to hand over the data. The court records were kept sealed.

"At one point, the US government threatened the imposition of $250,000 in fines per day if we refused to comply," Bell said.

Since the Snowden leaks, Yahoo and others have been seeking to make public these court documents to show they were forced to comply with government requests and made numerous attempts to fight these efforts.

BDST 0750 HRS, SEP 12, 2014