Twitter revealed on Wednesday that government demands for information about users rose in the first half of this year, with US authorities accounting for more than three-quarters of the requests.

Governments submitted a total of 1,157 requests for information about Twitter accounts, with 78 percent of those queries coming from the United States, according to a transparency report issued by the globally popular one-to-many test messaging service.

Twitter reported that it gave US authorities what they sought in 67 percent of the cases.

Japan was second when it came to requesting information from Twitter during the first six months of 2012, accounting for eight percent of the total.

The number of requests from governments has risen in each of the three Twitter transparency reports issued since the San Francisco-based firm began publishing them last year.

Twitter said the requests typically were made in connection with criminal investigations and lamented that it was barred by law from revealing anything about information demanded through US national security letters.

"An important conversation has begun about the extent to which companies should be allowed to publish information regarding national security requests," Twitter legal policy manager Jeremy Kessel said in a blog post.

"We have joined forces with industry peers and civil liberty groups to insist that the United States government allow for increased transparency into these secret orders."

Apple, Facebook, Microsoft and other top Internet and technology companies have come under heightened scrutiny since word leaked of a vast, covert Internet surveillance program US authorities insist targets only foreign terror suspects and has helped thwart attacks.

US lawmakers last week vowed to step up their campaign against government surveillance programs after narrowly failing in a bid to end spying practices they have decried as unconstitutional.

Twitter said that the number of requests by governments to remove user content rose to 60 from 42 in the prior six-month period, and just six in the first transparency report issued in July of last year.

"Governments generally make removal requests for content that may be illegal in their respective jurisdictions," the report explained.

"For example, we may receive a court order requiring the removal of defamatory statements, or law enforcement may ask us to remove prohibited content.

Meanwhile, notices to take down copyrighted material surged to 5,753 in the first half of this year from 3,268 in the last six months of last year, according to Twitter. gc/dc