VILNIUS, U.S.S.R., JAN. 9 -- Thousands of pro-Moscow demonstrators staged a second day of noisy protests around Lithuania's parliament here today amid reports of increased activity by Soviet military units in the breakaway Baltic republic.

At the same time, six light tanks and truckloads of Soviet Interior Ministry riot police surrounded the Vilnius television transmitting tower. The troops left after several hours without explaining their mission.

Lithuanian officials accused the Kremlin of manipulating the demonstrations and military maneuvers to create tension prior to a threatened Soviet army crackdown against draft resisters. The crisis atmosphere has been heightened by the sudden resignation Tuesday of the Lithuanian government headed by Prime Minister Kazimiera Prunskiene following the legislature's rejection of her economic-reform program.

Counter-demonstrators supporting Lithuanian independence later ringed the parliament building in response to a televised appeal from President Vytautas Landsbergis warning of a possible Soviet-backed coup attempt. The Lithuanian leader said he feared that the pro-Moscow protesters, mainly ethnic-Russian workers who fear discrimination by the Lithuanian majority, could try to take over the building by force.

"These days could be crucial. Our solidarity and determination are a dire necessity now," Landsbergis said in his telecast.

As the first of the three Baltic republics to declare independence from the Soviet Union last March, Lithuania seems the most likely point of open conflict now that Soviet President Mikhail Gorbachev has begun to reassert his authority. Its stand toward Moscow is more openly defiant than that of either of its Baltic neighbors -- Latvia and Estonia -- where attempts are underway to reach some kind of compromise with the military over the conscription issue.

Lithuanian officials said they had unconfirmed reports of Soviet military patrols seizing several draft-age Lithuanians on the streets of Kaunas, the capital during Lithuania's brief independence between the two world wars. Soviet soldiers were reported to be visiting private homes in Kaunas and Vilnius, the current capital, instructing draft evaders to report to conscription centers by next Sunday or Monday.

The Lithuanian defense department, which has organized a paramilitary force of several thousand unarmed volunteers, reported that a Soviet military aircraft landed at Vilnius airport today with about 50 paratroops. A column of 50 trucks filled with Soviet soldiers also was reported moving toward the Lithuanian capital from the direction of Latvia.

A similar increase in military activity took place last March after the newly elected Lithuanian parliament proclaimed the restoration of its pre-World War II independence and outlawed conscription of the republic's citizens into the Soviet army. That crisis ended in a political stalemate, with the central authorities using an economic blockade to prevent Lithuania from implementing its independence declaration.

In the Latvian capital, Riga, spokesmen for the republic's parliament said they feared that members of Interfront, an anti-independence group comprised mainly of ethnic Russians, could storm or vandalize the legislature during a rally called for Thursday morning. Interfront has protested the Latvian government's economic austerity measures, especially its plans to increase meat, bread and dairy prices, and has called a general strike for Monday.

Latvian President Anatolijs Gorbunovs has scheduled meetings with regional military leaders in an effort to head off a confrontation over the conscription issue. Gorbunovs wants the military to take into account alternative service performed by young Latvians in lieu of military duty. As in Lithuania, Latvian legislators are concerned that widespread arrests and investigations of draft resisters could end in violence.

Here in Vilnius, the Russians demonstrating outside parliament today shouted slogans demanding the imposition of direct rule from Moscow in Lithuania and the suspension of local government bodies. They dispersed following an appeal by the Russian Orthodox archbishop of Vilnius to avoid a conflict with the Lithuanian militia.

Lithuanian nationalists staged a vigil outside the parliament building tonight, singing Lithuanian hymns and waving the national flag. Inside the building, dozens of burly youths dressed in the black uniform of the Lithuanian National Guard lounged about, ready to repel any attack. Their only visible weapon appeared to be firehoses, which they used yesterday to repel demonstrators who managed to break down the front door.

"We will defend our independence. If we don't get what we want now, we are never going to get it," said one Lithuanian activist, in black boots and a black beret.

The initial pretext for the demonstrations organized by Russian organizations in Lithuania was a government decree raising prices on many essential commodities to phase out state subsidies. Parliament suspended the price rises yesterday, provoking the resignation of prime minister Prunskiene.

{In Kiev, capital of the Soviet Ukraine, the Associated Press reported that Soviet authorities have arrested Oles Donij, president of the Ukrainian Student Union, on charges of organizing the takeover of three university buildings during a student hunger strike that forced the resignation of the Ukraine's prime minister last October.}