Apple on Tuesday released details of government requests for its data while protesting a "gag order" that limits what can be disclosed about US national security orders.

The iPhone and iPad maker followed the lead of other US tech giants and released its first report on requests from governments around the world.

Most of the requests involve criminal investigations into "robberies and other crimes or requests from law enforcement officers searching for missing persons or children, finding a kidnapping victim, or hoping to prevent a suicide," Apple said in a seven-page document.

In the United States, Apple said, "the US government has given us permission to share only a limited amount of information about these orders, with the requirement that we combine national security orders with account-based law enforcement requests and report only a consolidated range in increments of 1000."

The document said Apple received between 1,000 and 2,000 US government requests between January 1 and June 30 of this year, affecting between 2,000 and 3,000 accounts.

It was unable to provide details on how much, if any, data was disclosed, saying this happened in a range of zero to 1,000 cases.

"We strongly oppose this gag order," the document said, adding that Apple has been pressing for greater ability to disclose the figures.

"Despite our extensive efforts in this area, we do not yet have an agreement that we feel adequately addresses our customers' right to know how often and under what circumstances we provide data to law enforcement agencies."

Apple added that "dialogue and advocacy are the most productive way to bring about a change in these policies, rather than filing a lawsuit against the US government."

But the company said it filed an amicus brief with the secret Foreign Intelligence Surveillance Court in support of others seeking greater transparency.

Apple said that it has never received a request under the controversial Section 215 of the Patriot Act, which gives the government broad electronic surveillance authority, and added that "we would expect to challenge such an order if served on us."

Outside the United States, Apple said it received several hundred requests, including 127 in Britain, 102 in Spain, 93 in Germany, 74 in Australia and 71 in France.

"We have reported all the information we are legally allowed to share, and Apple will continue to advocate for greater transparency about the requests we receive," the statement said.

The report comes with US tech companies under pressure following revelations of a secret government program that scoops up vast amounts of data from Internet firms.

Tech firms including Microsoft, Google and Facebook have been seeking to release more information on government data requests, in the belief this would reassure customers.