On the ground floor of a six-story building in Tripoli, agents working for Muammar Qaddafi once sat in an open room, spying on emails and chat messages with the help of technology Libya acquired from the West, The Wall Street Journal reported Tuesday.

The recently abandoned room was lined with posters and English-language training manuals stamped with the name Amesys, a unit of French technology firm Bull SA, which installed the monitoring center. A warning by the door bore the Amesys logo. The sign read: "Help keep our classified business secret. Don't discuss classified information out of the HQ."

The room provided clear new evidence of foreign companies' cooperation in the repression of Libyans under Qaddafi's almost 42-year rule. The surveillance files found there included emails written as recently as February, after the Libyan uprising had begun.

One file, logged on Feb. 26, included a 16-minute Yahoo chat between a man and a young woman. He sometimes flirted, declaring that her soul is meant for him, but also worried that his opposition to Qaddafi made him a target.

"I'm wanted," he wrote. "The Qaddafi forces ... are writing lists of names." He said he was going into hiding and would call her from a new phone number -- and urged her to keep his plans secret.

More On This...

"Don't forget me," she wrote.

This kind of spying became a top priority for Libya as the region's Arab Spring revolutions blossomed in recent months. Earlier this year, Libyan officials held talks with Amesys and several other companies including Boeing's Narus, a maker of high-tech internet traffic-monitoring products, as they looked to add sophisticated web-filtering capabilities to Libya's existing monitoring operation, people familiar with the matter said.

Libya sought advanced tools to control the encrypted online-phone service Skype, censor YouTube videos and block Libyans from disguising their online activities by using "proxy" servers, according to documents reviewed by WSJ and people familiar with the matter. But Libya's civil war stalled the talks.

The sale of technology used to intercept communications is generally permissible by law, although manufacturers in some countries, including the US, must first obtain special approval to export high-tech interception devices.

Libya is one of several Middle Eastern and North African states to use sophisticated technologies acquired abroad to crack down on dissidents. Tech firms from the US, Canada, Europe, China and elsewhere have, in the pursuit of profits, helped regimes block websites, intercept emails and eavesdrop on conversations.

Amesys in 2009 equipped the Tripoli monitoring center with "deep packet inspection" technology, one of the most intrusive techniques for snooping on people's online activities, according to people familiar with the matter.

Chinese telecom company ZTE Corp. also provided technology for Libya's monitoring operation, people familiar with the matter said. And VASTech SA Pty Ltd, a small South African firm, provided the regime with tools to tap and log all the international phone calls going in and out of the country, according to emails reviewed by WSJ and people familiar with the matter.

It is unclear how many people worked for the monitoring unit or how long it was operational.