By Stephen Gibbs
BBC correspondent in Havana
The Cuban government has closed most shops selling goods in dollars.
Queues formed outside dollar-stores in Cuban cities
It says it is an emergency measures in reaction to United States' proposals to tighten its embargo on the country.
US President George W Bush last week gave his backing to various measures designed to hasten the end of Fidel Castro's rule in Cuba.
The moves include a reduction in the amount of money Cuban Americans are allowed to take to their families on the island.
Thousands of shops across the country were shut on Tuesday.
Department stores that sell furniture, electrical equipment or hardware all had their doors firmly closed.
In the morning crowds milled outside. A heavier than normal police presence was noticeable.
Some Cubans were staring at the signs reading "closed until further notice" with an air of disbelief.
Since the dollar was legalised in the early 1990s, dollar stores have become the only places for them to buy not just luxuries but some essentials too, particularly clothes.
Shortages in local-currency shops are frequent in Cuba
Cuba has given no detailed explanation for shutting the shops - beyond that faced with US aggression, it is necessary to conserve resources.
Long queues have formed outside dollar stores that sell food. They have been allowed to stay open but some wonder for how long.
There is an air, encouraged by the Cuban government, that this country is getting on a war footing
Dissidents have expressed dismay at the whole turn of events.
They say that President Bush's declared aim to speed up political change here has given President Castro the perfect opportunity to create a sense of crisis in the country and they warn that a wider clampdown may yet come.