(Reuters) - A Chinese telecommunications equipment company has sold Iran's largest telecom firm a powerful surveillance system capable of monitoring landline, mobile and internet communications, interviews and contract documents show.

The system was part of a 98.6 million euro ($130.6 million) contract for networking equipment supplied by Shenzhen, China-based ZTE Corp to the Telecommunication Co of Iran (TCI), according to the documents. Government-controlled TCI has a near monopoly on Iran's landline telephone services and much of Iran's internet traffic is required to flow through its network.

The ZTE-TCI deal, signed in December 2010, illustrates how despite tightening global sanctions, Iran still manages to obtain sophisticated technology, including systems that can be used to crack down on dissidents.