The Iranian government, determined to defend itself against cyberattacks and limit Western influence, appears to have laid the technical foundations for a national online network that would be detached from the Internet and permit tighter control over the flow of information.

Iranian officials and outside experts say that development of the network has accelerated after cyberattacks aimed at the country's nuclear program.

Last month, Iran's communications and information technology minister unveiled a plan to take key government agencies and military outfits offline and onto the new network by the end of September. U.S. security researchers say they are for the first time seeing evidence of an operational network that is consistent with Iran's publicly stated plans.

The researchers say in a report to be released this week that they have found functional versions of the sites of government ministries, universities and businesses on the network. They also found evidence of an already operational filtering capability.

At the core of the network was high-end equipment manufactured by the Chinese firm Huawei that is capable of sophisticated online surveillance of traffic. The network is already "internally consistent and widely reachable," concluded the report, a copy of which was provided to The Washington Post.

The findings are likely to worry Internet freedom activists and the Obama administration, which has spent tens of millions of dollars on initiatives designed to ease access to the Internet in Iran and other countries with repressive governments. Officials had expressed concerns even before the release of the latest research.

A protected Iran-only network could help officials counter U.S.-funded programs that allow Iranian activists to evade online surveillance.

It could also help insulate Iranian computers from a covert campaign of cyberattacks that Iranian officials assert the United States and Israel continue to wage.

The Iranian network is not expected to entirely replace the Internet.

But for ordinary Iranians it could be a well-run alternative to the Internet, which in Iran is often still accessed through dial-up connections.

Internet speeds in the country are intentionally suppressed to make certain Web activities, including the streaming of video, virtually impossible. Many websites, such as Facebook and YouTube, are blocked by the Iranian government.

Having the infrastructure for a skeleton Iran-only Internet in place would give the Iranian government greater power to shut off access to the Internet at times of civil unrest, such as the anti-government protests that swept Iran in 2009.

Both the Obama administration and Internet freedom experts have expressed concern that the launch of the Iranian network could set a precedent for repressive governments across the globe.

"We don't want governments to believe that it is now legitimate to take a country offline," said Brett Solomon, executive director of AccessNow.org, a global digital freedom initiative.