Soviet authorities are tightening the screws on national and religious dissent in the Baltic republics, Estonia, Latvia, and Lithuania. The authorities officially admit there are serious ''deficiencies'' in the loyalties of the three non-Russian peoples whose independent states were absorbed by the Soviet Union more than 40 years ago.
Exile sources fear there will be new arrests among a group of loosely linked nationalist and unofficial peace activists in Latvia and Estonia. And in Lithuania, Roman Catholic priests have been imprisoned for the first time in more than a decade.
The latest development in Latvia is the postponement of a planned show trial of two young Baptists, Janis Rozkalns and Janis Veveris. Both men are accused of anti-Soviet activity and possessing religious and human rights documents. They face up to seven years' imprisonment.
The trial was scheduled to start Oct. 26 and last through Nov. 10. No reason was given for putting off the proceeding, but Latvian exile sources suspect publicity in the West may have had something to do with it.
Another factor could be Yuri Andropov's health. Authorities in Latvia aren't sure to whom they will have to account if they push ahead with the trial - and put an additional blot on the Soviet Union's international human rights record.
The latest arrest was of Gunars Astra on Sept. 15. On that day Astra testified at the trial of his friend Ints Calitis, a Latvian peace activist who signed an appeal for a Baltic nuclear-free zone and was sentenced to six years imprisonment a few days later. It is thought that Astra was arrested for something he said at the trial.
In Estonia, two activists, Endel Ratas and Erik Udam, fear imminent arrest. They signed an appeal for a nuclear-free zone including the Baltic statesas well as an open letter From Estonians to Finns warning that expansion of the capital port of Tallinn by Finnish companies will bring more Russians into Estonia.
Lithuania, too, has seen an escalation of repression. For the first time since 1971, priests have been imprisoned, according to Lithuanian sources in West Germany. Alfonsas Svarinckas was sentenced in May to seven years in a labor camp and three years' exile for membership in an unofficial Catholic committee to defend believers' rights. Another priest, Sigitas Tamkavicius, was arrested after testifying at Svarinckas' trial and is awaiting trial.
The repression in Latvia is the worst that has come to light there in more than 20 years, according to Julijs Kadelis, who runs an information clearinghouse for the World Federation of Free Latvians in Munster, West Germany. Estonian and Lithuanian exiles also speak of a greater crackdown on dissent since the passing of former Soviet leader Leonid Brezhnev. But they point out that the better-organized dissident groups in their countries have been persecuted since the late 1970s.
Official articles on ''ideological diversions'' against the Baltic republics show that widespread contempt for the Soviet system is alive among youth two generations after the ''establishment of Soviet power.'' On a less dramatic scale, this contempt has penetrated other segments of society like the cultural elite.
In Latvia, for instance, Communist Party chief A.E. Voss attacked the weekly Literatura un Maksia for publishing ''ideologically weak'' material. The journal often published articles about social and environmental problems and sometimes made oblique critical references to enforced orthodoxy in cultural life.
And in Estonia, there are many incidents of nationalist-tinged hooliganism, Estonian exiles in Sweden say. On Aug. 13, for example, 16-year-old Hannes Treinberg and an unidentifed companion were arrested for destroying a Soviet flag and hoisting the old Estonian national flag in the town of Juuru. In the Baltic seaside town of Pyarnu, an occasional stopover for buses carrying Western tourists to Riga, the capital of Latvia, from Tallinn, several students were accused of desecrating the gravestones of Soviet soldiers and officers at a local cemetery.
Information about Latvia is more sketchy, but emotional protests such as flag raisings and candle burnings on the graves of prewar Latvian statesmen occur there as well. Tourists report that a poster of Yuri Andropov labeled ''Wanted'' in English was put up on the bulletin board of a police station in the seaside resort of Jurmala, near Riga in early September.
In Lithuania, at least 15 underground periodicals circulate - although the existence of some is known only from references in the publications that reach the West. These cross-references are evidence of a critical dialogue among dissident groups.
There is, at least on some levels, a democratic political culture alive in Lithuania, giving it the most advanced and deeply rooted dissident movement of the three Baltic states. Thousands of citizens have signed petitions in support of persecuted priests or other church causes - making the political appeals signed by a few dozen Latvians and other Balts seem minor by comparison.
Most Western analysts agree that the main cause of national tensions in the Baltic states is the rapid influx of immigrants from other Soviet republics, mainly Russia. The demographic changes - brought about by flight to the West and Soviet deportations - are widely perceived as a policy of deliberate Russification.
Statistics from the 1979 Latvian census show that of the seven largest cities and towns in Latvia, only one had a majority of ethnic Latvians, compared to four cities with Latvian majorities in 1959. And in Estonia, the proportion of non-Estonians increased from just over 25 percent in 1959 to 35.3 percent in 1979.
A major reason for the influx to the Baltics has been the rapid industrialization of the region under Soviet rule. New industries and the work ethic of their Baltic peoples gave Latvia and Estonia the highest postwar standard of living in the Soviet Union during the 1970s.
But relative prosperity has not erased past traumas inflicted on the Balts under Soviet rule. Between 1940 and 1953, it is estimated that the Baltic states lost around 30 percent of their pre-World War II populations to deportations, wartime flight, and deaths in conventional and postwar guerrilla combat.
Young people contrast the experiences of grandparents or parents in Siberian labor camps with official histories that make passing reference to ''violations of socialist legality during the cult of personality.'' But the Soviet regime continues to suppress any open discussion of the past and portrays the interwar independence period in pejorative terms.
This has led to preoccupation with a distorted past. The Soviet Baltic regimes snatch at every historical straw to stress heroic efforts for Soviet Motherland and communism in World War II. Balts in the homeland and abroad cling to romanticized images of the prewar period and are still haunted by the Soviet takeover.
But hopes for a softening of internal and international dialogue about their nations' most painful problems have been dimmed by East-West tension and former KGB chief Andropov's rise to power.