SOFIA, Bulgaria--An outbreak of Slavic nationalist protest against the Turkish minority appears to be an attempt by Communist hard-liners to preserve their power in Bulgaria, an opposition leader said yesterday.

"It's an organized process from lower and middle levels" of the Communist Party, "and even some people at the top," said Petko Simeonov, a leader of the opposition Club for Glasnost and Democracy.

Thousands of nationalists in the past week have staged strikes and demonstrations in at least eight cities across Bulgaria to protest a Dec. 29 decision by central authorities to restore cultural and religious rights to the country's estimated 1.5 million Moslems, mostly ethnic Turks.

For years, ethnic Turks were subjected to a harsh assimilation policy under which they were forced to adopt Bulgarian names and to speak Bulgarian.

When former leader Todor Zhivkov was ousted Nov. 10, he was succeeded by Petar Mladenov who promised to steer Bulgaria out of its Stalinist past and into a democratic future.

However, the outburst of anti-Turk sentiment is embarrassing Mladenov's government and could upset the talks planned for Jan. 16 between the Communists and the opposition on reforms and the free elections Mladenov promised by May.

The protests "could push the country in a neo-Fascist and nationalist direction," said Simeonov. "This problem could deform the democratic processes in Bulgaria and postpone the talks."

The regional branch of the independent trade union Podkrepa in southern Haskovo and Kardzhali, where some of the most vehement ethnic protests occurred last week, claims that local officials commandeered buses and cars, megaphones and flags for the protests.

Opposition leaders and Western diplomats say the deep mistrust between nationalist Slavs and ethnic Turks has been fanned since the mid-1980s by Zhivkov's assimilation policy and by anti-Turkish propaganda.

Konstantin Trenchev, a leader of the Union of Democratic Forces, an umbrella opposition group, said he doubts the hard-liners can retain lasting influence, given the radical changes in Eastern Europe.

"They cannot exist alone in the world, isolated between East and West," he said.

Senior Communist leaders, opposition members, representatives of the Turkish minority and Slav nationalists met yesterday to try to defuse the situation. On Monday, they called for an end to further large protests or strikes and the tensions appear to have eased.

But the bitter hostility between Slavs and ethnic Turks is deeply ingrained and ready to flare up at the slightest provocation. A few dozen anti-Turk demonstrators gathered again yesterday around the National Assembly, or parliament, in Sofia.