The latest Internet blockade affected the most common form of secure connections, including all encrypted international websites outside of Iran that depend on the Secure Sockets Layer protocol, which display addresses beginning with "https."

"Email, proxies and all the secure channels that start with 'https' are not available," said a Tehran-based technology expert who declined to be identified.

"The situation regarding accessing these websites is even worse than last week because the VPNs are not working."

Many Iranians use virtual private network, or VPN, software to get around the extensive government Internet filter which aims to prevent access to a wide range of websites including many foreign news sites and social networks like Facebook.

Last week, millions of Iranians suffered serious disruption in accessing email and social networking sites amid concerns the government is extending its surveillance on ordinary citizens.

Iranians have grappled with increased obstacles to using the Internet since opposition supporters used social networking to organize protests after the disputed 2009 re-election of President Mahmoud Ahmadinejad.

The government denied any fraud in the vote which ignited large-scale street protests that were crushed by security services after eight months.

Iran is preparing to hold parliamentary elections on March 2, the first national election since 2009.

(Reporting by Zahra Hosseinian and Ramin Mostafavi; Writing by Amran Abocar; Editing by Sami Aboudi)

• A Permanent Economic Emergency