Russian artillery and aircraft pounded the Chechen capital today in the aftermath of an apparently disastrous ground assault on the city that reportedly left more than 100 soldiers dead and dimmed the aura of invincibility army commanders had tried to project during three months of warfare in the separatist region.

In Moscow, officials heatedly denied that a pitched battle had occurred in Grozny, but the wall of denial was soon eroded by Russian news agencies, which reported clashes with heavy Russian losses. AVN, an unofficial military news agency, said officials in Mozdok, the staging area for Russian military operations, acknowledged that 50 soldiers had been killed overnight in central Grozny. It said they had entered the city in 15 armored vehicles--eight tanks and seven armored personnel carriers--from Khankala, a small town at the city's southeastern edge.

The Interfax news agency said that an army "intelligence unit" was ambushed in Grozny's downtown Minutka Square and that Chechen defenders killed 25 soldiers and captured four armored vehicles. "This reconnaissance operation was aimed at identifying bandits' firing and fortified positions in eastern Grozny," Interfax quoted its sources as saying.

A spokesman for Russia's Federal Security Service, a successor to the Soviet KGB, called reports that 100 Russian troops had died "misinformation," but he added that there may have been a "reconnaissance in force" operation in Grozny. He said such a probe by a small unit would not have resulted in heavy casualties. Reporters in Grozny for the Associated Press and the Reuters news service said they counted the bodies of more than 100 Russian soldiers after the battle.

Heavy army casualties in Chechnya--such as the large-scale losses suffered in the Chechen war of 1994-96--could have political implications on the eve of Sunday's Russian parliamentary elections. Prime Minister Vladimir Putin, who is backing a slate of candidates, has staked his political future on the course of the war, and his popularity has soared over the last three months. A military fiasco could provide ammunition for his political opponents.

Russian news reports about Wednesday's clash in Grozny, crediting unidentified sources, conflicted with the official version. Deputy Army Chief of Staff Gen. Valery Manilov said categorically: "No Russian armored vehicles have entered the city." Defense Minister Igor Sergeyev called reports of a debacle in Grozny "lies and misinformation." The Russian military reported that only two soldiers were killed in Chechnya in the past 24 hours.

Whether a high death count will deflate public support for the army offensive in Chechnya is an open question. Many Russians regard Chechnya as a nest of Muslim terrorists who pose a threat of internal violence and threaten the cohesion of the Russian state.

Today, former prime minister Yevgeny Primakov said that if reports of the Russian military defeat are true, it would constitute a "crime." Like Putin, Primakov is a candidate for president in next year's elections. "It is a crime to send untrained troops into such an attack, or to carry out an unprepared action which may lead to great losses," he said.

Primakov went on to criticize the issuance of contradictory information by the government and the military. "The defense minister says there has been no assault on Grozny and this won't happen in future. Then another fairly high-ranking military chief says that as long as there are still civilians there, there won't be an assault on the city. A third says the operation will be completed, by and large, before the end of the year. A fourth says it may take until February. I get the impression that these operations have not been thought out in advance," he said.

Reports from Grozny said the battle went on for three hours in and around Minutka Square, a traffic circle about two miles from the center of the capital. Afterward, the bodies of scores of Russian troops were said to be strewn among the charred chassis of Russian tanks and other armored vehicles. Streets nearby are framed by high and mid-rise apartment buildings, and the column appeared to have been targeted from all sides.

Russian forces shelled Grozny through Wednesday night and this morning, and the blasts could be heard as far away as the Ingushetia border, another Russian region 30 miles west. At Mozdok, Su-24 and Su-25 ground-attack jets took off every few minutes, headed either for Grozny or targets in Chechnya's mountainous south.

In another development, Russian officials have been warning repeatedly that the Chechen rebels are preparing home-made chemical weapons for use in against Russian troops in Grozny. Such a tactic would be risky for the Chechens, who would presumably be engaging the Russians in close quarters. At the same time, Russian commanders might be tempted to launch similar weapons from afar.

Maj. Gen. Nikifor Vasilyev, a chemical warfare expert, told reporters today that the Chechens are preparing weapons made of "poisonous chemicals, chlorine, ammonia and sulfuric acid.

"Bombs packed with these substances are being buried in a number of districts of Grozny," he said. "The bandit command is actively engaged in constructing chemical obstacle fields along the likely lines of advance of the federal forces."

Russian officials also launched a broadside at the foreign media today. The Federal Security Service spokesman said that reports from Grozny are "nothing but a part of a black public relations campaign that is being carried out by foreign secret services with the help of correspondents."