6 Lithuania Guards Die at Border : Violence: In Azerbaijan, a mighty explosion tears through an express train, killing 14. The KGB brands it ‘sabotage.’

Unidentified raiders armed with automatic weapons struck a Lithuanian border post early Wednesday, killing six guards loyal to its secessionist government, while in the troubled Soviet south, a mighty explosion--branded “sabotage” by the KGB--tore through an express train and killed at least 14 passengers.

The violence, still unexplained and almost certainly not coordinated, revived a pattern of domestic bloodletting and tensions that seem to surge whenever President Mikhail S. Gorbachev steps into the world limelight--as he has this week in his summit meeting with President Bush.

Many Soviets see the episodes as attempts by die-hard right-wingers and the army, the KGB security agency and police to discredit or publicly humiliate Gorbachev.

Details were still sketchy about the explosion aboard Train No. 6, bound from the Soviet capital to the Azerbaijan city of Baku. But the official Soviet Tass news agency said the blast occurred at 6:40 a.m. while the train was near Makhachkala, a town 220 miles north of Baku on the western shores of the Caspian Sea. The blast killed at least 14 passengers and injured 16. Tass quoted the local KGB chief as calling it an “act of sabotage.”

In Lithuania, the republic’s leader implicated a special police unit of the Interior Ministry in the killings of the border guards.

The attack was “a political provocation of right-wing forces with the purpose of casting a shadow on the Moscow summit,” Lithuanian President Vytautas Landsbergis asserted.

When asked who killed the guards, he said, “it was either OMON or the Mafia,” referring to the special Interior Ministry unit or organized criminal gangs. “Or possibly, the two acted together,” he added.

Andrei V. Kortunov, a top analyst at the USA-Canada Institute, said: “The fact that it’s purposeful, synchronized with President Bush’s visit to Moscow, is undeniable.”

Six gray-uniformed guards at a small, one-story wooden building at Medininkai on the frontier with Soviet Byelorussia were shot, point-blank, in the head, and left to die, according to journalists who went to the scene. Grisly film of the scene was shown on television Wednesday evening.

Spent cartridges from Kalashnikov automatic rifles--according to some reports, the same type of firearm as those issued to Soviet soldiers--littered the floor. Three pistols and three submachine guns belonging to the guards were missing.

Lithuanian officials said the dead were three customs officers, two members of the republic’s own police force and a traffic police officer. Two other men were gravely wounded. The victims were found by truck drivers who stopped at the post about 25 miles east of Vilnius on Wednesday morning.

Gorbachev told reporters he received only sketchy information on the deaths in Lithuania as he met with Bush earlier at his presidential retreat outside Moscow. Speaking in general terms, he blamed enemies of his policies for the blood spilled, saying, “The more productive the dialogue is, the more incidents and efforts there are to destroy it.”

The United States has never recognized the Soviets’ forced annexation of the Baltic republics in 1940, and Bush on Tuesday called on Moscow to allow Lithuania, Estonia and Latvia to be free. But at his news conference with Gorbachev, Bush refused to “prejudge” the border incident and said it would be “unfair” to link it to Lithuania’s 1 1/2-year push for independence.

Gorbachev, who expressed sympathy for the families of the victims, told reporters that Vladimir A. Kryuchkov, the head of the KGB security police and intelligence agency, has offered to assist in an investigation of the Medininkai deaths. “I will be monitoring this and will tell you what happened,” Gorbachev assured reporters.

Those statements will be of little comfort to most Lithuanians, since the last investigation by central authorities of killings in the Baltic state--a whitewash of the Soviet army’s tank-backed onslaught in January that killed 14 people--claimed Lithuanian nationalists alone were responsible. An expose printed here has even implicated the KGB in the operation.

Speaking at a hastily convened press conference in Vilnius, the Lithuanian capital, Landbergis accused the United States of not doing enough to push Gorbachev and the rest of the national leadership into recognizing Lithuania’s independence.

The Interior Ministry denied any involvement in the slayings. Boris K. Pugo--the minister who is in charge of the OMON detachments but says those units, known here as “black berets,” have escaped from his control--said he was “shocked.” He promised to do all he could to track down those responsible.

As news of the deaths spread, a crowd gathered outside the building of the anti-secessionist Lithuanian Communist Party, shouting, “Murderers! Bandits!” The parliament scheduled an emergency session for today. The World Lithuanian Games, which had brought together athletes of Lithuanian origin from around the world, were suspended.

The Kremlin has opposed the customs and border posts erected by the independence-minded Baltic republics as unconstitutional, and since January, the installations have been a frequent target of attacks by the police commando units. The posts have been burned down or their staffs have been beaten. But in January, commandos in Latvia shot and killed five people when they raided the Interior Ministry headquarters there.

Lithuania demanded last week that OMON forces leave the republic. Russian President Boris N. Yeltsin, who signed a treaty with Landsbergis on Monday formalizing ties between their republics, condemned what he called the “crime” at Medininkai and--without accusing the OMON units--demanded their withdrawal from Lithuania.