During Russia's long war in Afghanistan, Russian soldiers who were perplexed by rebel hit-and-run tactics took to calling their adversaries "the spirits," to describe a vaporous enemy that made Houdini-like escapes from tight spots.

Here in Chechnya, where Russia is fighting its third anti-guerrilla war in 20 years, the spirits are back. In the eastern town of Argun on Sunday, rebels appeared as if from nowhere and fired on Russian troops bottled up in buildings. After the Russians trained heavy artillery on Argun, the fighters disappeared.

Residents said the attackers came and left by car and jeep, but no one seems to know from where they came or to where they retreated.

"How they got in, I don't know. How they got out, I don't know," said Rasmagomed Boltugayev, an old man who wobbled down an empty Argun street today. "They can come when they want. It was easy."

"The rebels come in and no one bothers them," said Ibrahim Barayev, a merchant. "I have to pay a bribe at checkpoints to leave the city!"

The assault on Argun and at least seven other towns during the past two weeks marked the beginning of a new phase in the nearly four-month-old Russian ground offensive. For the first time, Russian forces are not calling the shots. Sly rebels, using the cover of darkness and fog, slip behind Russian lines to upset the tranquillity that Moscow promised would follow its invasion of the rebellious region. They also resisted the Russian advance on the besieged capital of Grozny.

The recent attacks made good a rebel pledge that, once Russia had rolled over the plains and low hills of Chechnya, guerrillas would strike the occupation force again and again.

It is too early to tell whether the war is at a definite turning point. In the first Chechen war, from 1994 to 1996, rebels also harassed the Russians. However, it took many months of warfare, supplemented by terror attacks inside Russia, before the Chechens ousted the Russians and won Chechnya its virtual independence from Moscow.

Moreover, compared with the last war, Chechen society appears to be more divided and fatigued. While the Russians are not loved, many of the guerrillas are far from admired. Three years of chaos here, in which banditry and kidnapping reigned, dented the guerrilla mystique.

In any event, the post-Christmas attacks drowned out Russian predictions of a quick end to major combat.

"We are in this for a long time," said a Russian colonel at military headquarters in Mozdok, just beyond the Chechen border. "It is obvious that we have to find ways to defend ourselves better. The question is, Why don't we know how by now?

It took four days for the Russians to reclaim Argun and supposedly "cleanse" it of rebels. Russian fatalities totaled between 14 and 20, depending on who is asked. Yet, even today, tension was pervasive. Reporters who visited Argun with Russian military escorts were warned repeatedly about snipers. Russian sharpshooters took up positions at each stop of the tour.

[The Interfax news agency, citing sources in the Russian military command in Chechnya, said 33 Russian soldiers had been killed in the past 24 hours. Until recent days, Russian forces had claimed losses of no more than one or two soldiers a day.]

Among Russian soldiers and many Chechen residents in Argun, the prospect of further combat created a sullen mood. Soldiers who would have been confidently discussing the imminent fall of Grozny a few weeks ago now ponder survival in the treacherous Chechen night.

The main rebel attack on Argun began on Monday at 9 a.m. and lasted 12 hours. Guerrillas surrounded several points where Russians were concentrated: the railroad station, a police motor pool, another auto service garage and an administration building. Estimates for the number of rebels varied from 150 to 600.

At the railroad station, "they shot from all directions," said Capt. Palukh, a military police officer in charge there. "They yelled at us to surrender. They said they would give us free transportation to Moscow." Four of his troops died in the assault.

Ruslan Asmandirov, a soldier at the motor pool, described sniper fire from a nearby school. "They just drove up, and when it was over, they drove away," he said.

Fighting eased Tuesday, and on Wednesday Russian military police swept the town for stragglers.

The ease with which the rebels entered Argun gave rise to Russian suspicions that they were assisted by civilians. Certainly, the soldiers said, no one tipped the Russians off to an impending attack.

The Russians are nominally allied with a local militia in Argun--clans as well as prominent or wealthy Chechens usually possess private armies. But such is the level of mistrust that the Russians collected their allies' rifles and machine guns, leaving them only pistols to defend themselves. "They said they were only taking the arms to register them. But that was weeks ago, and I haven't seen my automatic since," said Ayub, a young Chechen who aspires to learn German and emigrate.

Argun is an industrial town once inhabited by 30,000 people. It sits along the main highway east from Grozny on a plain between the Terek River and the foothills of the towering Caucasus mountain range and was a frequent battleground during the last war. Most industry was destroyed. Empty grain elevators are defaced by bullet holes and grenade blasts. Metalworks and electronics factories have been turned into skeletal, charred ruins.

Residents say that after the last war, Argun became a crossroads for smugglers. Their talents help guerrillas move among the back roads and ditches.

"No one has ever really controlled Argun, and no one will. To think otherwise is a fantasy," remarked Saidpudin Khamedov, an engineer who was loitering in the yard of a hospital. Only the trauma ward was functioning. The laboratory wing was hit by Russian shells during the recent fighting.

Many civilians say they are trapped between suspicious Russians and disruptive guerrillas. In particular, the presence of Islamic extremists among the fighters upsets Chechens whose brand of Islam is a blend of Muslim and local customs. They claim, along with the Russians, that many Islamic fighters are mercenaries from abroad. "They don't even speak Russian, much less Chechen," said Leza Vachigayev, who works at a tiny drug dispensary.

Downtown, where Moscow's representative to Chechnya, Nikolai Koshman, was giving residents a pep talk, women berated him for the artillery barrage that drove the rebels out. "Kill the terrorists, not us," they shouted.

The Russian soldiers looked on impassively. "These women show up every time we have visitors," one murmured. "Who can tell the terrorists from anyone else? I can't."