A new law has been passed in Cuba which will make access to the internet more difficult for Cubans.
Cuba's licensed internet terminals are meant only for tourists
Only those authorised to use the internet from home like civil servants, party officials and doctors will be able to do so on a regular phone line.
The bill says the state telephone company Etecsa will use technical means to detect and impede access.
Correspondents say the law will affect thousands of Cubans who access the
worldwide web from their homes.
It took effect on Saturday, according to a letter sent by Etecsa internet service E-net to customers.
The government says the move is necessary to "regulate dial-up access to internet navigation services, adopting measures that help protect against the taking of passwords, malicious acts, and the fraudulent and unauthorised use of this service".
The Cuban Government passed a decree last year that the internet could only be accessed using a more expensive telephone service charged in US dollars, not generally available to ordinary Cubans.
E-net customers who do not have the dollar phone service can still access the internet legally by buying special cards at Etecsa offices.
Some Cubans also can use international email and a government-controlled intranet at work and in schools.
But until now many people have been using computers and internet accounts borrowed or bought on the black market, and it is they who will be affected by the new law.
The previous system allowing access to the web granted many Cubans a rare opportunity to observe western media and news reports.
Global television news channels are only available at luxury hotels which are off limits to Cuban citizens.
It is feared that as well as "blacking out" this window on the world, the new move to further limit web access could also damage Cuba's main source of foreign revenue: the tourism industry.
Thousands of ordinary Cubans have relied on the internet to advertise private accommodation for foreign tourists.