Saying Russian troops have suffered from "tenderheartedness" toward Chechen civilians, Russia's military commander in the Caucasus said today his forces will detain Chechen males between 10 and 60 and take them to a holding camp to check whether they have ties to rebel forces in the breakaway region.

The declaration from Gen. Viktor Kazantsev described a broad crackdown by the Russian military and intelligence services designed to curb rebel incursions on Russian-held territory in Chechnya that in the last two weeks have stripped the Russian offensive of its victorious sheen. This is an important point, Russian commentators say, because the image of a low-cost conflict must be maintained to ensure Acting President Vladimir Putin's widely anticipated victory in the presidential vote scheduled for March 26.

Kazantsev acknowledged what he portrayed as mistakes and naivete in the defense of three towns east and southwest of Grozny, the besieged Chechen capital. Among the mistakes, he said, were troops' "tenderheartedness" and "groundless trust" in Chechen civilians. As a result, the Russians did not thoroughly search houses, where presumably guns and ammunition, and perhaps rebels themselves, were hidden, he added.

"Now we are compelled to correct these mistakes," he said. The decision: "Only children aged up to 10 and men over 60, and women, will henceforth be regarded as refugees."

Males between 10 and 60 will be ferried to a Chechen "filtration camp" in Chernokozovo he said, where they will be checked for guerrilla affiliation. Kazantsev also announced that a nighttime curfew has been imposed, although a curfew was ordered in Russian-controlled parts of Chechnya when the ground offensive began in September.

Officials said "precision helicopters" also are being deployed to assault rebel hiding places with more accuracy than either artillery or airstrikes have been able to attain.

Sergei Ivanov, the head of the Kremlin's advisory Security Council, also promised a crackdown by the Federal Security Service, Russia's domestic intelligence agency, and by Interior Ministry officials in Chechnya. In effect, Russia's hearts-and-minds campaign, designed to win over Chechens by providing pensions and electricity, appeared to be coming to an end.

"First of all, this is connected with intensification of activity and hardening, if you wish, of the activity of law enforcement bodies," Ivanov said, "so that the local population sees that order has come--for a long time and forever."

The measures announced today seemed to reflect an assessment that the recent rebel attacks on Russian positions are technical problems that can be resolved by fine-tuning the Russian war machine and increasing surveillance.

Until mid-December, Russia's overwhelming firepower and commitment of 100,000 troops rolled back the fractious Chechen rebels. But Russia's winning streak ended with its inability to seize Grozny, which has been bombarded for four months. The smooth ride was further upset by guerrilla incursions into three towns west of the city last week and, on Sunday, into three Russian-controlled towns to the east and southwest--Gudermes, Argun and Shali.

Russian officials said today all three towns are back under Russian control, although only Shali was shown in television broadcasts. There, soldiers and paramilitary police said they were besieged in their command posts by rebels who demanded their surrender. The Russians resisted until the rebels withdrew. The Russians said the rebels suffered heavy casualties--up to 150 dead--but no bodies were shown.

Russian commentators have begun to compare the current situation to Russia's first war in Chechnya, from 1994 to 1996, which ended with a Russian withdrawal and effective independence for Chechnya.

"The troops do not control the territory of Chechnya. They simply stand in separate camps and defend themselves," wrote the newspaper Moskovsky Komsomolets. "All this happened before. The '94-'96 war, during which . . . entire Chechnya was 'under full control.' "

Almost nightly on Russian television, soldiers give harrowing accounts of the guerrilla actions. Karen Paloyan, speaking from a hospital in Volgograd, said his unit was ambushed when it tried to rescue a convoy that was attacked and set afire.

"Somebody opened fire from a grenade launcher. We were hit twice. We were all thrown off our armored vehicle. Then we were fired on by snipers," he said.

CAPTION: Russian soldiers prepare to fire a mortar on rebel positions in Chechen capital of Grozny. Moscow is moving to curb rebel raids into Russian-held territory.