DOLINSKY, Russia (AP) _ Russian planes rained flyers today on the Chechen capital with an ultimatum to rebel fighters and civilians still holed up in the battered city: Leave or be destroyed.

The Russian command warned that anyone in Grozny had until Saturday to flee before federal forces unleashed a massive artillery and air bombardment to smash the city into submission. It said a safe corridor would be open until Dec. 11 to let civilians escape.

``Persons who stay in the city will be considered terrorists and bandits and will be destroyed by artillery and aviation. There will be no further negotiations. Everyone who does not leave the city will be destroyed,'' the flyers said.

Russian forces have been bombing and shelling Grozny for weeks in an attempt to dislodge rebels entrenched in the city. But as Russian troops have tried to tighten their encirclement of Grozny, the rebels have put up greater resistance.

Russia has previously offered civilians a corridor out of Grozny, but it has never been clear how residents would be able to safely flee the regular air and artillery attacks. Most of the residents who remain are old and infirm, or too scared to leave.

But the Russian military appears unwilling to risk storming Grozny, for fear that street battles will result in the kind of heavy casualties Russian troops suffered in the city in the 1994-96 war.

Russian forces also claim to have blockaded Grozny and control the main roads to the city. Still, Chechen fighters say they can freely move in and out of Grozny, bringing in supplies and ammunition when necessary.

An Associated Press reporter outside Grozny had no trouble moving through the widely-space Russian positions around the city. At night, large numbers of Chechen fighters and others were seen moving in and out of Grozny.

Russia quickly seized control of a third of Chechnya when the campaign began in September, easily sweeping down across the republic's northern plains. Russian forces now control more than half of Chechnya.

Russian jets and helicopters attacked targets around Chechnya today, while rebel fighters put up heavy resistance in Argun _ a key eastern city that Russian commanders claimed to have captured last week.

Russia's NTV television reported that Russian forces had taken control of one district in Argun, located nine miles east of Grozny, but had not defeated militants holed up in the town center and other districts. Russian officers in Chechnya also said that rebels still held large parts of Argun.

Also, the Russians have not yet tried to occupy the mountainous area south of Chechnya, where they would be vulnerable to attacks by Chechen guerrillas.

Russia's initial, upbeat forecasts of a quick victory have been revised, with commanders now saying they expect a longer, harsher war.

Russia pressed ahead with its air campaign today. Russian Su-24 bombers and Su-25 attack planes flew 67 sorties in the last 24 hours, targeting the rebel stronghold of Urus-Martan and the villages of Vedeno, Shali and Shari-Yurt, officials said.

Russian attack helicopters ran 47 sorties in Chechnya, with Russian officials claiming the airstrikes destroyed 23 vehicles, three communications facilities and several other targets, as well as damaging a bridge.

Russian forces entered Chechnya in September following incursions by the militants into Dagestan. The militants have also been blamed for apartment bombings in Russian cities that left 300 people dead.