Cleaning out the Soviet `mafias'. Kremlin whispers suggest that Vladimir Shcherbitsky (right), Ukrainian party boss and Politburo member, will soon be axed - the latest move in Mikhail Gorbachev's drive to rout opposition to reform. But the Soviet leader faces great risks. When he removed the party leader of Kazakhstan republic, nationalist riots ensued. In the Ukraine, where nationalist feeling runs high, Shcherbitsky loyalists could cause trouble.

Mafias. That's the word Soviet officials use privately, but with increasing frequency, to describe the Communist Party organizations of Soviet Kazakhstan and the Ukraine.

Operations are already under way against the Kazakhstan party structure of Dinmukhamed Kunayev, whose removal as first secretary on Dec. 16 was followed by large riots.

Oleg Miroshkin, the second secretary of the Kazakhstan party, was removed Saturday, and other lesser officials were also fired last week.

Over the weekend, it was further announced that a much-criticized regional party leader from another part of the Soviet Union, Voronezh, in the Ukraine, had been removed: Voronezh First Secretary Vadim Ignatov. Mr. Ignatov, like Mr. Miroshkin a Brezhnev-era appointee to the Central Committee, was replaced with an official of the central party apparatus.

And there is no longer any doubt about whether Mikhail Gorbachev will move against Vladimir Shcherbitsky, the party chief of the Ukraine. The only question is, when?

Mr. Shcherbitsky's main weapon against being sacked is that he heads the most powerful regional party organization in the country. But a second weapon he could use to preserve his position, Ukrainian nationalism, may already have been neutralized by the leadership in Moscow.

As it takes its first steps to clean up the Kazakhstan party organization, Moscow seems to be clearly signaling to other leaders that playing the nationalist card will not work.

The official news media here are consistently stressing that the recent upsurge of Kazakh nationalism was the product of two factors: complacency and incompetence by the republic leadership, and a deliberate effort by the leadership there - Mr. Kunayev is never mentioned by name - to use nationalism to shore up its position.

The Communist Party youth newspaper Komsomolskaya Pravda on Saturday described in detail how the disturbances in the capital of Kazakhstan, Alma-Ata, had been organized. After a plenum of the Kazakhstan party in December, the paper says, some opponents of political and economic reform felt themsleves threatened. Unable to oppose the changes openly, they adopted ``another slogan - nationalism,'' the paper says.

It is not clear whether the Alma-Ata disturbances resulted in any deaths. A senior Western diplomat who asked not to be identified by name told journalists last week that he had heard of injuries, but not fatalities. Most of those injured, the diplomat said, were police, who had been ordered not to use their weapons.

Kunayev is expected to be removed from the country's ruling Politburo at the next plenum of the party Central Committee. The plenum, already long overdue, may be held this week, although no date has yet been announced. The Moscow rumor mill, currently working overtime, has suggested that Shcherbitsky may go at the same time, and perhaps be replaced in the Ukraine by Viktor Chebrikov, the KGB chief who was once a party worker in the Ukraine. General Chebrikov is an ethnic Russian.

Dismantling the Ukrainian structure may, however, take more time. Kazakhstan has a population of 16 million, but the Ukraine is as big as a West European country: 50 million people.

If the Ukrainian party leadership decided to use nationalism as a weapon, the problems for Moscow could be serious indeed.

The Ukrainians have a separate language, a well-developed literature, and a history that predates Moscow or the northern Russian city-states. They also have a long tradition of nationalist sensitivity.

Serious criticism of the Ukrainian party organization is, however, intensifying, though it has yet to attack Shcherbitsky or any senior lieutenants by name. The latest example of this appeared last week in the main Communist Party newspaper, Pravda. It described the efforts of a senior Ukrainian party official, actively assisted by senior police officers, to force a local journalist into making false accusations against another journalist who had written articles harshly critical of Ukrainian party officials. The party officials named in the latest story, one Soviet observer said, were ``known Shcherbitsky men.''

The story was quickly followed by a letter on the front page of Pravda from Chebrikov.

The official named in the earlier piece, Chebrikov noted, was the KGB chief for the area. He and several other KGB officers had been replaced and disciplined, Chebrikov said.

The letter was the first instance that observers here could remember of a KGB admission of abuse of power.

It was also a stark illustration of the reach of the Ukrainian party ``mafia.'' But the speed with which Chebrikov moved against his own organization presented a sharp and perhaps embarrassing contrast with Shcherbitsky's inaction in such circumstances.

These articles were only the latest in a steady stream of criticism.

Last month, for example, a report on the state of the harvest in the Ukraine noted the poor performance of recent years.

``Weather conditions,'' Pravda noted, ``are by no means wholly to blame for this.''

The departure of Kunayev and Shcherbitsky, whenever this happens, will not spell the end of opposition to Gorbachev's reforms.

The intermediate level of the bureaucracy seems to be largely passive, if not hostile to the reforms, which threaten their comfortable existence.

And the continuing delay in calling the Central Committee plenum indicates that differences of opinion - at the very least on the speed and emphasis of Gorbachev's reforms - persist at the top of the Soviet Communist Party leadership.