The Russian assault on the Chechen capital Grozny is meeting heavy resistance, as rebel forces hit back with ambushes and sniper fire.

The Russian Itar-Tass news agency quoted generals as saying that their forces had raised the Russian flag over a district in the north-west of the city.

They were also maintaining control over an important bridge across the Sunzha River.

But elsewhere, they appeared to have made little headway, as fierce house-to-house fighting was reported around the central Minutka Square.

Grozny has been under air and artillery bombardment for months, and Russian troops have been advancing on the ground for several weeks.

But federal forces have yet to wrest control of the city centre from the rebels.

The Russian Emergencies Ministry said several hundred civilians had escaped from Grozny at the weekend, but up to 20,000 - mostly the old and infirm - are believed to remain in the city.

Air operations

Elsewhere, Russian warplanes and helicopter gunships continued to pound suspected rebel bases, flying more than 100 missions in 24 hours, according to the Interfax news agency.

Air operations were particularly intense in the Argun and Vedeno gorges in southeastern Chechnya.

Russian forces have captured the large Chechen village of Vedeno, which lies on a strategic rebel supply and escape route and has been under sustained attack for weeks.

But guerrillas still maintain bases in the steep gorges, which are almost impenetrable in winter.

No deadline

Russia's Acting President Vladimir Putin, preparing for a presidential poll election in March, said on Sunday that he would not push troops in Chechnya to end the campaign by any specific date.

"The timing of the operation is fully decided by military considerations," Mr Putin said. "It will not be timed to any date on the political calendar."

The four-month offensive in Chechnya has made Mr Putin the most popular politician in Russia and the strongest candidate in the presidential polls called for March 26.

Earlier, a senior Kremlin official announced that the body of a Russian general had been found in a trench close to where he led soldiers in his last attack.

He said there were bullet holes in the body. There is no independent confirmation of the discovery.

Major-General Mikhail Malofeyev, who was commanding a unit in Grozny, was reported missing last week. Chechen rebels said they had captured and interrogated him.

He was the first Russian general to have been killed in action since federal forces entered Chechnya last October.

Maskhadov denial

Chechen commander Mumadi Saidayev meanwhile denied Russian reports that Chechen President Aslan Maskhadov had been wounded.

Saidayev said he had spoken to President Maskhadov on Sunday and that he was well.

Mr Maskhadov's wife Kusama also denied the Russian reports. She said her husband was in good spirits and committed to crushing the latest onslaught.

"We believe that victory will be ours," she said.