Web users in Iran have reported a sharp reduction in internet speed and a lack of access to several prominent websites.
The Entekhab website reports on Friday that internet speed has been severely reduced for several hours, and access to Yahoo and Facebook has become impossible.
The report adds that that in the early hours of last Wednesday morning, the internet was completely cut off for several hours all across the country.
The Human Rights Activists News Agency reports that on Thursday, sites that use SSL protocol for security could no longer be accessed.
SSL is an industry-standard security technology used by websites to protect online transactions with their customers.
HRANA indicates that the disruption of internet services coincides with the efforts made by the Intelligence Ministry to access the personal emails of Iranian internet users, with an eye to cracking down on government critics and protesters.
The service fluctuations coincide with the approach of the anniversary of the February 14 protests and the house arrest of Iranian opposition leaders.
Some opposition groups have issued a rally call to Iranians to join a silent march on that day.
Sign up for the Eurasia Review newsletter. Click here to have Eurasia Review's newsletter delivered via RSS, as an email newsletter, via mobile or on your personal news page.