AS SUBWAY BOMBING BOOSTS FEARS, 100,000 ATTEND YELTSIN CONCERT.

Byline: Alessandra Stanley The New York Times

As security measures tightened all over the city in the wake of Tuesday's deadly subway bombing, more than 100,000 people Wednesday celebrated Russia's declaration of independence from the Soviet Union in 1990 by attending a boisterous rock concert for President Boris Yeltsin. It was his biggest rally in Moscow since his rise to power in 1990 and 1991.

The helicopters, armored personnel carriers and hundreds of police and security service officers who patrolled the political pop concert alongside Red Square were a sign of heightened tension four days before the presidential election.

But the huge turnout was an astonishing display of support for Yeltsin, whose tarnished record and hated war in Chechnya have cut deep into his popularity even among pro-democratic voters in Moscow.

As the day of reckoning approaches, the mood of many voters in Moscow has shifted from jaded passivity to focused attention and even alarm. For the last two weeks, newspapers, television and politicians of all stripes have been warning darkly of civic disturbances and threats of violence.

Communists are pre-emptively asserting that Yeltsin will either steal the election or refuse to abide by its results. The Yeltsin campaign, buttressed by reports in mainstream Moscow news organizations that openly favors it, has been keeping up a steady drumbeat of accusations that the Communists will disrupt the voting at the polls, or even try to overthrow the government by force.

Wednesday both sides seized on the subway bombing to ratchet up the anxieties of voters. The explosion, which ripped apart a Moscow subway car Tuesday night, killed four people, and left 12 seriously wounded, has not yet been explained.

``They tried to scare us yesterday by an explosion in the metro,'' shouted Yeltsin, addressing the crowd that spilled out of Red Square and over a bridge across the Moscow River. ``Those scoundrels who want to disrupt the election are prepared to go that far. The Motherland will not forgive them. They have no future.''

Earlier, Yeltsin warned, ``The best response to the machinations of extremists will be a vote on June 16, a vote for civil peace, for stability, for the future of Russia.''

At a somber, frills-free rally for young Communists, party standard-bearer Gennady Zyuganov said the bombing incident was a direct result of Yeltsin's inability to maintain order, calling his tenure ``the politics of chaos.'' But, edgy and defensive in the face of accusations by the Yeltsin camp that his party is intent on violence if defeated, he repeatedly told his audience of 4,000 that he plans to abide by the election outcome.

The Communist candidate carefully avoided suggesting what some of his supporters and aides said Wednesday, namely, that the bombing was a ``provocation'' deliberately set by forces loyal to Yeltsin to scare voters away from voting for the Communists.

But Viktor Ilyushin, a Communist Party leader and chairman of the Committee for Security in Parliament, said he could not rule out the possibility that the bomb was set to ``destabilize the Russian situation on the eve of the elections.'' He said he thought the administration might use the incident to ``start repression against the opposition.''

Spokesmen for the Russian Federal Security Service, a branch of the former KGB, said that the bomb, which exploded Tuesday night in a subway car 400 yards from the Tulskaya metro station, about 3 miles from the Kremlin, was a homemade high-explosive bomb equivalent to about a pound of TNT.

Though the investigation is still in progress, the security service characterized it as a ``politically-motivated terrorist act,'' for which no one has taken responsibility.