Shake-Up Certain, Czech Official Says : East Bloc: As hundreds of thousands rally in Prague, a party leader asserts that ‘real changes’ will be made. The leadership meets in emergency session today.

More than a quarter of a million people jammed into Prague’s main square Thursday in a rally to support opposition demands for political change, as a senior Communist Party figure announced that a shake-up in the party’s hierarchy is imminent.

Prague party chief Miroslav Stepan, also a member of the ruling Politburo, told a group of factory workers in the capital that an emergency party Central Committee meeting scheduled for today will produce “real personnel changes.”

The Central Committee has the power to replace members of the Politburo, including hard-line party leader Milos Jakes.

Stepan’s comments were made amid signs that a major power struggle has been played out within the Communist Party’s hierarchy. Although doubts remained regarding the outcome, there are signs that reformists may have won the day.

Meanwhile, police and the party’s own militia reportedly occupied state-run Czechoslovak television during the day Thursday, but by evening, they had withdrawn. Also believed to have withdrawn from the capital are militia units that had arrived Wednesday, triggering rumors that Jakes might use them to force an end to the weeklong crisis.

The party daily Rude Pravo carried an article criticizing “the lack of flexibility of the hierarchy, which failed to deal with the crisis situation.”

Jakes has been under growing pressure as anti-government demonstrations on an unprecedented scale have shaken the regime. His resignation, along with those of five other senior party hard-liners, is a key demand of the political opposition.

There is mounting speculation that Jakes himself may be forced out today, although some believe he could attempt to dump others from the Politburo first in an effort to save himself.

“Jakes is under attack from all sides,” said one Communist Party official with links to the Central Committee.

While the 150-member Central Committee is heavily weighted in favor of hard-liners, the intensity of the pressure for change is said to have led a number of members to support turnover.

“There are lots of ‘yes, yes’ men in there, but already many are swinging around,” the Communist Party official said. “There are lots of strange bedfellows at the moment.”

Jakes heads one of the last hard-line Communist governments in Eastern Europe. His position has become increasingly precarious since the fall of East German hard-liner Erich Honecker last month.

A Czechoslovak Communist Party adviser indicated that Jakes also has come under fire from Moscow, with Soviet President Mikhail S. Gorbachev reportedly demanding that the Prague regime move ahead with reform.

Jakes reportedly met Thursday with the Soviet ambassador to Prague, Viktor Lomakin.

Despite the pressure on Jakes, some analysts warned that his departure is not a foregone conclusion.

“It’s premature to say the game is over,” one Western diplomat cautioned.

Jakes himself appeared to show no sign of wavering, telling a group of party workers and trade union organizations in northern Czechoslovakia that he “will use political means to halt the negative development in society.”

Still, party leaders will have to take more than token action to defuse mounting support for a two-hour, anti-government general strike planned for Monday, diplomats said.

At Thursday’s rally, opposition leader Vaclav Havel announced that more than 500 industrial concerns had pledged support for the strike. The stoppage was called by the recently formed opposition group Civic Forum to press its demands for the resignation of hard-liners and punishment for those responsible for police violence against student demonstrators last Friday.

Although students and intellectuals in many large cities are backing the strike, the support of the workers is vital if it is to succeed.

The massive rally Thursday, by far the largest to date, clearly gave the fledgling opposition coalition a powerful emotional boost.

A bit of graffiti sprayed onto a wall near the square summed up the mood of the largest rally since protesters began gathering in force one week ago: “Victory.”

At one point, the crowd clapped to the rhythm of the American black spiritual, “Let My People Go.”

In what one analyst called Havel’s first purely political speech, the dissident playwright pleaded for greater support for the strike.

“The strike may decide whether we start on the road to democracy or whether an isolated group of people will win who want to keep all others out--people who want to keep power by mouthing empty slogans of reconstruction,” he said.

In addition to an appeal to workers to join the strike, Havel also said the Civic Forum remains prepared for a dialogue with the government to chart the country’s future.

He called on the police and the army “to join the people and, if necessary, defend them. We want to live in a free, democratic Czechoslovakia. . . .”

At the same rally, the leader of the small Socialist Party, Jan Skoda, allied himself clearly with the opposition, even though his party remains technically linked to the Communists as a member of a national front that rules.

“We consider this party again as independent and free,” he said. “Our first task today is a renaissance of the democratic process. . . .”

The opposition received a further boost when former party leader Alexander Dubcek addressed a pro-strike rally of about 10,000 people in the city of Bratislava.

A letter from the architect of the country’s 1968 liberalization was read at Wednesday’s rally in Prague, and there were rumors he plans to speak at an opposition rally here.