Exclusive The Sultan of Oman's intelligence services are spying on the local operations of British oil company Shell with the aid of controversial European tech companies, the Register has learned.

Documents seen by el Reg reveal that the internal phone systems at Petroleum Development Oman (PDO) - a joint venture between the Omani government and various Western energy companies including Shell - have been tapped on behalf of the Sultan's intelligence service. The work was carried out by two notorious European firms specialising in "lawful interception" of communications: Gamma International and Trovicor.

Gamma has frequently been embroiled in controversy in recent years, particularly after it was found to have been touting for business from the former Egyptian President Mubarak's notorious secret police.

The company has also been implicated in surveillance of Ala'a Shehabi, a journalist, university lecturer and human rights activist from Bahrain, now living in London – as well as human rights activists based in the UAE and Turkmenistan. Gamma's “FinFisher Suite” (which includes Trojans to infect PCs, mobile phones, other consumer electronics and servers, as well as technical consulting) is regarded as some of the most advanced interception technology available on the commercial market.

Gamma was already known to have a relationship with the Omani regime, generally thought to be primarily aimed at surveillance of the local population's communications. However it has now emerged that the company is also specifically targeting foreign organisations, including British ones like Shell. In addition, the documents reveal that a commercial operation in Oman being conducted by Blighty's Oxford University - the setting up of Muscat University - is also being specifically targeted by Gamma and Trovicor on behalf of the Sultan's spooks.

Trovicor, acting as sub-contractor to Gamma in spying on PDO and Muscat Uni - according to the documents seen by The Register - was recently named as an “Enemy of the Internet” by freedom of speech watchdog Reporters Without Borders. The firm has been questioned over its human rights record, in particular during a hearing before the European Parliament Subcommittee on Human Rights in 2010 about its engagement with the governments of Iran, Bahrain and Syria – each notorious for torture and imprisonment of journalists and dissidents.

Formerly a sub-division of Nokia Siemens Networks, in 2009 Trovicor was “spun out” as a German firm, maintaining branches in Dubai and Islamabad, as well as Switzerland, the Czech Republic and Lebanon. The company's Beirut office, according to the documents, is responsible for work in Oman.

The documents show how Trovicor and Gamma International were jointly tasked in 2010 to install a new piece of telecommunications equipment which would listen in on all phone calls made at PDO. The content of the calls would then be delivered to a “monitoring center” believed to be operated by the Omani intelligence services.

Shell owns a 34 per cent interest in PDO, in a “production sharing agreement” with the Omani government, who own sixty percent of the firm. Overall, PDO is responsible for extracting most of the country's gas supply and around 70 per cent of its oil reserves.

Numerous current and former Shell engineers and management staff, known for their expertise in delivering long term energy projects, are seconded to or directly employed by PDO, and are using the phone systems listened into by the Omani security services. These include Managing Director Raoul Restucci, who was previously Executive Vice-President for Shell in the Middle East and North Africa Division.

Though the company is joint owned, industry insiders with experience working on similar “production sharing agreements” say the ability of the Omani government to listen in on the phone conversations of Shell employees seconded to PDO could prejudice regular commercial negotiations between the two parties over the sharing agreement.