HAVANA -- A high school teacher commenting on Cuba's recent crackdown on crime and dissent stops suddenly to ask, ``What's Castro afraid of?"

A mere rumor of another Mariel exodus sends 2,000 people rushing to the seaport.

``Everyone is afraid. Everyone is nervous, says economist Oscar Espinosa." And a well-known Cuban author whispers to a visitor, ``It's the end of the millennium, and you know the troubles that brings."

Havana is in an anxious mood these days, with Cubans and resident foreigners alike saying their collective apprehensions stand at levels not seen since Cuba's economy hit bottom in 1994.

The capital today seems virtually under siege. Police from elite units check IDs of passersby at most main corners, and Cubans who once met openly with foreigners now seek private encounters and speak in whispers.

Prostitutes who jammed the seaside Malecon boulevard have been hauled away to ``reeducation camps." Police are even seizing illegal but long-tolerated TV antennas capable of receiving Miami broadcasts.

Two new laws have imposed tougher jail terms and even death sentences on criminals. And a new category of counterrevolutionary felony was created -- ``supporting hostile U.S. policies."

Castro has said the reasons for the curbs are simple: Crime was getting out of hand, and too many dissidents were accepting U.S. aid to ``subvert the revolution."

Some find this a credible explanation, but there's also a growing sense in Havana that the ground under Cuba's Communist system has shifted in recent months -- shifted subtly, yet in ways that Castro, common people and foreign analysts alike view as potentially troublesome.

``Everyone I talked to there has the intuition that there's something more than what is said in public," said Joaquin Roy, a University of Miami expert on Cuba's Spanish heritage who visited Havana last month.

But in Cuba, an opaque society where ``public opinion" is practically nonexistent, finding answers requires much reading between the lines.

At first glance the island appears to be continuing its recovery from the ruin it faced after billions of dollars in Soviet subsidies stopped flowing in 1991. Cubans today look better fed and clothed than three years ago. There are more cars on the streets of Havana and more new construction. A good number of colonial-era buildings, many on the verge of crumbling, are being repaired.

Furthermore, the government is increasing salaries for some state employees for the first time in years, and its recent move to strengthen the peso, from 21 to 20 pesos per dollar, increased the purchasing power of families on an island where most goods are now priced in dollars.

``Compared to '93 and '94, when we had 20-hour electricity blackouts, no gas to cook with and just rice and sugared water to eat, we're better off," said retired engineer Miguel Angel Fuentes.

Yet that progress pales when compared to the cocktail of afflictions that Cubans, and foreigners living in the country, say is fueling a climate they call ``restless," ``anxious" and ``uneasy."

Rumors in January that Castro would again open the port of Mariel swiftly drew 2,000 people to the area, two witnesses said. Several scuffles with police broke out, and Interior Ministry troops were called in to block off all surrounding roads for two days.

Loss of control

Behind the crackdown lies a recent acceleration in the government's loss of control over people, Cubans and foreigners say, a process that began when Castro was forced to accept economic reforms and slash subsidies on goods in 1993.

``This is a battle against everything that means disorder, crime, disrespect for authority, illegal business and lack of social controls," said one government official in describing the reasons for the constraints.

Subsidized food rations that once lasted 15 days out of every month now last barely 10 days, Havana residents said, forcing them to go to the far more expensive farmers' markets to shop for food.

With an estimated 30 to 40 percent of all Cubans now surviving on dollars sent by relatives abroad, mostly in South Florida, the government has lost much of its power to command the loyalty of its people.

``The government is no longer the only source for the little things that it traditionally used to control the populace -- food, a new TV, a fan, a pair of shoes, said a Latin American diplomat in Havana.

``With dollars in your pocket, you can tell the [Communist] Party to go away when they want you to go to some demonstration," said restaurant waitress Victoria Gema.

Haves vs. have nots

Some Cubans indeed believe the latest crackdown was demanded by party, military and government officials who are unlikely to get remittances from Miami and feel angry that the ``dollarized Cubans now eat and dress better than they do."

``Those who are loyal to Castro now get the least benefits. And those who are least loyal, those who look to Miami, live the best," said a Western journalist who has lived in Havana for several years.

But Cubans complain that party, military and government leaders have been making up for this drawback by accepting bribes to overlook illegal activities from prostitution to people smuggling.

Low-level corruption, long a necessity for getting around Cuba's socialist inefficiencies, has blossomed into a more Western version of high-level graft and racketeering, they argue.

``Before, we all had friends in high places who did favors. Now we have mafias at the highest levels, an insult to everyone who sacrificed for this revolution," said a worker who claimed to have surrendered his party card last year to protest a hushed-up corruption scandal at his factory.

Economic frustration grows

Cubans are beginning to realize that the timid economic reforms Castro adopted in the eight years since he declared a ``special period in time of peace" -- a euphemism for the island's post-Soviet crisis -- cannot resolve its basic problems.

``They are all just patches on an old tire," said Espinosa.

``Although the economy looks good, it's all cosmetic," added another Western journalist living in Cuba. ``The real problems have not only not been addressed, they are not even being thought about."

The absence of hope for economic recovery in the near future appears to have increased the level of frustration among many Cubans.

``Until last October or so, most Cubans would tell me they were resigned to the fact that no change would happen until Castro dies," said a Canadian businessman who lives in Havana. ``Now they say that's too long. They are restless, and they talk more about the need for change."

In an apparent blunder, the government raised the credibility of dissidents when it televised the prosecution's final argument in the March 1 trial of four opposition leaders who include Vladimiro Roca, son of a late founder of the Cuban Communist Party.

``The son of Blas Roca! That's incredible!" said a Havana taxi driver. ``Here the government is always saying the counterrevolutionaries are nothing. But the son of Blas Roca, that's someone very important."

Cuban officials appear largely untroubled by Havana's mood, with one calling it ``the intended result of steps taken to cut short a series of unwanted phenomena that we had been seeing over the past six months."

And there's little evidence that the restlessness could easily translate into more serious trouble.

``Although the government can no longer dole out those little benefits -- the TVs and the fans -- it still has a big stick, a repressive machine that can stop any challenge to stability," the Latin American diplomat said.

That has not stopped Cubans from worrying, sometimes to an astounding degree.

One taxi driver was complaining about Havana's potholes last week when he stopped to make a seemingly disconnected declaration to a foreign passenger:

``When this is over, blood will flow in the streets."