WARSAW, JUNE 15 -- The trigger for this week's rebellion against the Romanian government in Bucharest was the use of police violence to clear a square blocked for seven weeks by pro-democracy hunger strikers. But the root cause of the protest was a feeling of betrayal, one that is sure to survive Thursday's onslaught of whip-cracking vigilantes.

The grievances that led thousands of young people to attack government buildings with gasoline bottles, cars and rocks have been festering almost since the day last December when an enigmatic former high-ranking Communist named Ion Iliescu stepped forward to take control of the revolution that toppled dictator Nicolae Ceausescu.

In the half-year since Romania's revolution, Iliescu's governing National Salvation Front has professed its democratic intentions but retained much of the Ceausescu government's style and players.

In the countryside, which gave Iliescu and the Salvation Front a landslide victory in the May 20 elections, these links are overlooked or silently endured.

But in the cities, among students, young families, intellectuals and office workers who fought and died for democratic change in December, the personal, political and philosophical ties between the front and the old Ceausescu regime have been a source of mounting anger.

Every evening during last month's election campaign, thousands of citizens came to central Bucharest's University Square to talk, sing protest songs and scrutinize blurry videotapes of the December uprising. The words changed night by night, but the message never varied: Iliescu and the front had hijacked the December revolution.

The demonstrators, and the more than 1 million Romanians who signed the anti-Communist Timisoara Proclamation, see Iliescu as a Communist masquerading in a democrat's clothes. They believe he plans to erect a system of reform communism where rigid Ceausescuism once stood.

Iliescu refers to himself as a social democrat, and since December has taken pains to appear a genial, mild-mannered conciliator. But since taking power six months ago he has been intolerant of criticism and reluctant to break with the habits and players of the past.

The National Salvation Front's list of parliamentary candidates during the recent election, for example, included many of the former regime's regional Communist Party bosses and several former close associates of Ceausescu himself.

Among them were Ion Avram, a former minister of heavy industry regarded as a close associate of Ceausescu, and Eugen Florescu, one of the dictator's chief propagandists, whom Iliescu appointed to oversee the country's newspapers during the election campaign.

Iliescu himself held ministerial rank in the Ceausescu government until 1984. Even after he fell out with the dictator, Iliescu kept his house in an exclusive Bucharest suburb reserved for high-ranking Communist Party officials.

During his current trial on charges of ordering demonstrators to be shot during the December revolution, Ceausescu's son Nicu was asked why he had decided to drive to Bucharest just hours after his parents had fled angry mobs there. Nicu Ceausescu, a regional party chief, answered without hesitation. He had heard that Iliescu had taken power, he recalled, before the prosecutor steered the questioning elsewhere. "I knew Mr. Iliescu from before, so I thought that everything would be all right."

Since the front consolidated power earlier this year, many local and county-level Communist officials have simply changed hats. "Now instead of sending reports to the party headquarters in Bucharest, they send them to the front," said Petre Bacanu, a senior editor of Romania Libera, the independent newspaper trashed on Thursday by pro-government vigilantes.

Iliescu's use this week of vigilantes to beat up demonstrators has drawn condemnation from the U.S. and British governments, but it was not the first time Iliescu has used thugs to intimidate opponents.

In February, then as now unable to count on the support of the army, he called in truckloads and trainloads of aggressive factory workers and former Communist Party thugs to intimidate tens of thousands of anti-Communist demonstrators. Then as now, the pro-government "workers" trashed the headquarters of opposition parties. In February, elderly opposition party leaders had to be evacuated by tank. This time, the vigilantes actually abducted the National Peasant Party's white-haired leader, Ion Ratiu, and held him for several hours. Ratiu was lucky. His assistant reportedly was one of hundreds who suffered severe beatings at the hands of the Iliescu supporters.

Last month, Iliescu presided over an election campaign marred by acts of intimidation and violent attacks on members of political parties other than his own.

Faced with opposition, Iliescu spouts the Stalinist rhetoric favored by his predecessors. In this lexicon, anti-government demonstrators first were "hooligans," the same word Ceausescu used for anyone who dared defy him. More recently, Iliescu has branded those who oppose him as "fascists," and suggested they are controlled by foreign journalists and governments.

How much any of this week's turmoil penetrates into the countryside is anyone's guess. Iliescu has kept the country's one television station under the front's control. It feeds viewers a heavy diet of rock music videos and on Thursday informed its viewers that the anti-government protesters took to the streets while high on drugs.

The Romanian audiences of Radio Free Europe and the Voice of America, which had fallen off since the December revolution, are said to have climbed back to pre-revolution levels. It was no accident that the first place the demonstrators tried to occupy was the television station.

"If everyone else in Europe can have free television, why is Romania different?" an angry airplane mechanic said at an anti-front demonstration after the election. "It is because they are proven liars, and soon they will show that they are killers, too."