The Russian military more than doubled the number of air attacks in and around the besieged Chechen capital today, but its ground units have not yet been able to break a fierce rebel defense of Grozny that has inflicted the highest rate of casualties on Russian forces in the four-month-old war.

Taking advantage of clear skies, Su-24 and Su-25 ground-attack jets along with helicopter gunships flew 250 sorties today--more than twice the number of each of the past three days. At the same time, Russian troops backed by intense artillery fire tried to press in on the city center; their immediate goal appeared to be Minutka Square, which is the hub of several main streets.

But the troops seemed barely to have moved forward from areas they have held for days in Staropromyslovsky, a northwestern district of Grozny, and a smaller city district in the east. Rebel spokesmen said their guerrilla detachments were striking at Russian forces behind the front lines, using snipers and ambushes to slow their advance.

Refugees from Grozny reaching Ingushetia, a Russian region west of Chechnya, described a seesaw battle in the capital, in which government forces move ahead yards at a time by day, only to retreat at night in the face of rebel ambushes. They say buildings in the city are being blasted again and again by Russian tank and artillery fire; some crumble under the onslaught, while those still standing are porous ruins.

Overall, the "final assault" on Grozny has diverged from the Russian script. An operation that was supposed to last three or four days has gone on for more than a week, and official Russian reports have become eerily repetitive. "Fierce fighting around Minutka Square" has become a daily chant of Defense Ministry spokesmen. Combat sites have been identified variously as Tukhachevsky and Kirov streets, sub-districts 1, 2 and 4, a university building, police headquarters, a central heating factory, a dairy, a cannery and a railway bridge.

The urban fighting has caused a surge in Russian casualties. The Interfax news agency said Monday that the Russian death toll in Chechnya had reached 926, a third more than official tallies. Of those, more than 500 are said to have died in December, when the first Russian attacks on Grozny were launched. Russian observers attributed the disparity in numbers to deception and bureaucratic accounting, which do not count deaths that occur in hospitals or fatalities among "contract soldiers," those who have signed up solely for the duration of the war.

Independent NTV television, which has been broadcasting increasingly incisive reports on the war, carried reports today from two military hospitals. In Samara, a soldier named Andrei who had suffered a head wound was unable to speak. It took military searchers a week to notify his relatives.

At Orenburg Hospital, 48 wounded soldiers had just arrived. "We were fighting for some plant," said a patient named Alexander Korotkov. "There are very many wounded. At first, we stayed very peacefully in a village, then we were brought to Grozny. I was hit by mine fragments, me and another guy. Both his legs were torn off. With me, it's the foot."

Nikolai Aldakov, a patient who had lost both feet, said: "I was pulling a wounded [comrade] from the battlefield. A sniper fired at me. The first bullets hit my armored vest, which saved me. He saw that and aimed at my feet. Their snipers are very skilled, and we are suffering huge losses."

Meanwhile, the Reuters news agency distributed a dramatic video made behind Chechen lines that depicted the capture of some Russian soldiers. On it, a bearded rebel shouts at the crew of a crippled Russian armored vehicle: "Freeze! Hands up! Fast! Hands up!"

A Russian in the vehicle responds: "It was an order. We were not even shooting. My automatic is lying on the ground. Not a single cartridge." Today's official Russian report on progress of the Grozny assault was slightly altered to reflect the apparent problems. Gen. Anatoly Kvashnin, commander of Russian forces in Chechnya, said the battle for Grozny "is developing according to plan"--the routine military description. But then he added: "It is not without some difficulties."

Gen. Vadim Timchenko, deputy chief of staff of the North Caucasus army, described rebel resistance as "vicious." "The enemy is well prepared," he said, while adding that the guerrillas are trying to escape the city.

The Russians say they are taking a heavy toll on the rebels, but official casualty estimates have attracted scornful press critiques. "If we sum up all official reports, almost 10,000 guerrillas have already been killed, and between 30,000 and 40,000 wounded," the newspaper Sevodnya wrote. "Last fall, all security ministries assured us that there could not be more than 40,000 guerrillas in all."

Russian officials say that 2,500 rebels are defending Grozny, a figure that has been unchanged for weeks, despite official reports that the city has been sealed off by Russian forces and that the guerrillas still in it are suffering scores of casualties daily.

Also today, the Russian army conducted a military funeral for Gen. Mikhail Malofeyev, who was killed on Jan. 18 in the battle for Grozny. He was the highest-ranking Russian casualty thus far in the war, and his death symbolized the ferocity of the struggle for the city. It has not yet been explained why it took five days to recover his body.

Gen. Vladimir Shamanov, who was relieved earlier this month as a senior field commander, said only that the rebels tried to take Malofeyev's body away "but that powerful artillery fire" forced them to leave it behind.

CAPTION: Russian troops use a tank for protection as they move cautiously forward against Chechen guerrillas who have been defending Grozny.