Two European companies — a major contractor to the U.S. government and a top cell-phone equipment maker — last year installed an electronic surveillance system for Iran that human rights advocates and intelligence experts say can help Iran target dissidents.

Nokia Siemens Networks (NSN), a joint venture between the Finnish cell-phone giant Nokia and German powerhouse Siemens, delivered what is known as a monitoring center to Irantelecom, Iran's state-owned telephone company.

A spokesman for NSN said the servers were sold for "lawful intercept functionality," a technical term used by the cell-phone industry to refer to law enforcement's ability to tap phones, read e-mails and surveil electronic data on communications networks.

In Iran, a country that frequently jails dissidents and where regime opponents rely heavily on Web-based communication with the outside world, a monitoring center that can archive these intercepts could provide a valuable tool to intensify repression.

Lily Mazaheri, a human rights and immigration lawyer who represents high-profile Iranian dissidents, said she had suspected that the government had increased its capability to monitor its perceived enemies.