In what appears to be the latest bid by a government to throttle access to news and information amid growing civil unrest, the Syrian government Friday shut down all Internet services.

Internet monitoring firm Renesys reported that starting around 7 a.m. EDT today, close to two-thirds of all Syrian networks were suddenly unreachable from the global Internet.

In just 30 minutes, routes to 40 of 59 Syrian networks were withdrawn from the global routing table, said Renesys' chief technology officer, James Cowie, in a blog post.

The shutdown has affected all of SyriaTel's 3G mobile data networks, as well as several of the country's ISPs, such as Sawa, iNet and RunNet.

Also down are the Damascus city government page and the customs website. The only networks that appear to be somewhat reachable are a handful of government-owned networks such as one belonging to Syria's oil ministry, Cowie noted.

"We don't know yet how the outage was coordinated, or what specific regions or cities may be affected more than others," Cowie wrote. "If Egypt and Libya are any guide, one might conclude that events on the street in Syria are reaching a tipping point."

According to The Washington Post, a government-sponsored website has confirmed that all 3G, DSL and dial-up services have been disconnected across Syria.

The shutdown comes amid growing civil unrest -- thousands of people took to the streets today to protest the death of a 13-year-old boy who was allegedly tortured and killed by Syrian security officials. The death of the boy and several other children recently has prompted calls for the resignation of President Bashar al-Assad.

Syria's move to pull the plug on the Internet is reminiscent of the actions taken by other governments in the region recently.

In January, Egypt imposed an unprecedented Internet blockade for several days in response to growing civil unrest.

In February, Libyan officials resorted to the same tactic to in an apparent bid to stop protesters from getting news and communicating with one another. That block was lifted relatively quickly, though.

Back in 2009, the Iranian government blocked Internet access for the same reasons.

The tendency by governments, especially in the Middle East, to shut down the Internet in times of crisis has evoked considerable concern among civil rights groups here in the U.S over free speech issues. The groups fear that the same thing could happen in the U.S.

Groups such as Demand Progress and the Computer and Communications Industry Association have in the past expressed alarm over proposals to give the president the power to shut down portions of the Internet in an emergency.

Others argue that the U.S Internet infrastructure is too big and diverse to be subject to the kind of total shutdowns witnessed in the Middle East recently.

Jaikumar Vijayan covers data security and privacy issues, financial services security and e-voting for Computerworld. Follow Jaikumar on Twitter at @jaivijayan, or subscribe to Jaikumar's RSS feed . His e-mail address is jvijayan@computerworld.com.