Soviets grope for answer to unrest. Moscow's crackdown in Nagorno-Karabakh Wednesday (Page 2) shows mounting concern over nationalist protests. Elsewhere, the Kremlin's policy is ambivalent - swinging from tolerance to deep suspicion.

The Soviet leadership's response to nationalist ferment is a mixture of improvisation, containment, and confusion. Some branches are responding with sophistication, others with suspicion or plain disarray. Communist Party leader Mikhail Gorbachev and his close associate Alexander Yakovlev appear to play the main role in formulating a new nationalities policy. Recent events in the Baltic states indicate that Yegor Ligachev, the second-ranking party leader, is less involved.

The new policy is still being worked through, but seems to be tending toward a relatively more conciliatory, flexible approach to minority nations.

In the case of the Baltic nations - Latvia, Lithuania, and Estonia, annexed by Moscow in 1940 - this will probably take the form of encouragement for newly formed mass movements, coupled with a warning that secession is totally unacceptable.

But events in Lithuania indicate that an influential branch of government, the KGB, is reacting with deep suspicion.

The response of communist leaders in republics affected by nationalist unrest has varied widely. In Estonia, the leadership has largely identified itself with the new mass movement, the Popular Front. Here, in Lithuania, the party leaders' reaction has bordered on panic.

Conversations in Moscow indicate the prevailing view within the Central Committee hierarchy is as follows: The formation in April of the Estonian Popular Front, the first of the Baltic mass movements, was generally welcomed in the party hierarchy. It was recognized that the movement included people who wished to secede from the USSR, but who did not constitute a majority. The best way to isolate them, this view held, was to push forward with practical reforms, not denounce the movement. But secession would be resisted by all means.

During the summer, Mr. Gorbachev and Mr. Yakovlev devoted particular attention to the Baltic states. In July, Gorbachev had what was later described as a long, substantive talk with the new Estonian Communist Party chief, Vaino Valyas. The reform-minded Estonian later told a radio interviewer that Gorbachev expressed support for the Estonian party's approach to the nationalities issue.

In August, Yakovlev traveled to Latvia and Lithuania. His Lithuania visit suggests that the party leadership is trying to reach out to the mass movements. Two days before he arrived, an official whom activists here describe as a Yakovlev aide met seven members of the Lithuanian Movement for Support of Perestroika (``restructuring'').

The official, interestingly, did not come from a new Central Committee subdepartment established to handle the nationality issue. Instead, he was from the Central Committee's Culture Department, which according to some observers has had close relations with Yakovlev.

One of the Lithuanians present at the meeting, Vytautas Landsbergis, recalls the official's saying he had come to obtain a better understanding of the new movement. So far, the official commented, Moscow had received only ``panic stricken'' descriptions of events in Vilnius. His listeners understood the source of these reports to be the party leadership. Dr. Landsbergis says the official also warned ``gently'' that the situation could turn into another Nagorno-Karabakh (the disputed Armenian enclave in Azerbaijan where a state of emergency was declared yesterday) if not handled properly.

Activists also say the Moscow official expressed the view that the new movement should have its own legal newspaper. This has since happened.

The activists in turn complained about the behavior of the Lithuanian Communist Party second secretary, Nikolai Mitkin, an ethnic Russian.

In Vilnius, Yakovlev met with the republic's various cultural unions, many of whose members are active in the Movement. Movement organizers were encouraged by his visit.

``It stabilized the political situation'' here,'' says activist Arvydas Juozaitas.

The Movement's information bulletin later quoted Yakovlev as expressing sympathy with some Lithuanian grievances about nationality policy and with the call for sovereignty. Last week, activists were told they would be allowed to obtain office space, a telephone, and other accouterments of an official organization. They attribute this directly to Yakovlev.

Confusion in nationalities policy is, however, visible even in the central leadership. Estonian party Second Secretary Indrek Toome told a magazine this week that the central television cut portions of an interview where he made favorable comments about the Popular Front. The Estonian and Lithuanian news media have published the secret protocols to the 1939 Ribbentrop-Molotov pact, which paved the way for Moscow's annexation of the Baltic states. But officials in Moscow still deny that a verifiable copy of the treaty exists.

The Lithuanian leadership's response to nationalist agitation remains ambivalent. Landsbergis refers to ``disarray'' in the party leadership, which has generally been hostile. Activists from Kaunas, the republic's second city, say party leaders are urging supporters to establish ``dummy'' sections of the Movement.

Several individuals in the party have indicated sympathy for the Movement. But the KGB appears to be taking no chances. On Aug. 30, the head of the Lithuanian KGB invited several of the Movement's main leaders to a meeting.

``Are you for or against Soviet power?'' activist Juozaitis remembers KGB Gen. Eduardas Eismuntas asking.

Movement activists claim they are kept under frequent KGB surveillance.

``They're working quietly, collecting information on us,'' one says. ``When the time comes they'll try to compromise us. They can always find something illegal that we've done. Perhaps the kids who put out the [Movement's] newspaper will turn out to have broken some rules buying newsprint.'' When he left a hotel he was followed. And on a visit to Lithuania, this reporter was under surveillance.