From DAVID LJUNGGREN

Grozny, Thursday

PRESIDENT Boris Yeltsin today extended by 48 hours his deadline for

Chechen separatist fighters to lay down their arms as the Russian

advance ground to a halt in thick fog.

A statement by Yeltsin said the people of the rebel republic had 48

hours from midnight to disarm in order to ''minimise the use of force

which could bring victims among the peaceful population''.

Russian troops earlier shelled Chechen forces north of Grozny and

closed in around the capital, with the most forward units only four

miles from the city limits.

Thick fog then forced them to halt their advance.

The Russian Government had vowed to crush Chechen fighters' resistance

if they failed to disarm today. However Chechens ignored the ultimatum,

and hopes of avoiding further bloodshed looked slim.

At least three farmers were killed today when a Russian helicopter

gunship opened fire on a farm near the settlement of Dolinskoye,

witnesses said.

Yeltsin's statement left open the chance of a negotiated settlement,

saying he would send a high-ranking Russian delegation to talks if

Chechen leader Dzhokhar Dudayev agreed to head his side's negotiating

team and the shooting stopped.

''If illegal armed formations cease fire, I will consider it a

manifestation of goodwill and the first step towards restoration of

peace and legality in the Chechen republic,'' said Yeltsin.

Dudayev also said he wanted talks, but insisted that Moscow first pull

out its troops. Russia has consistently refused to agree to such terms.

Russian Foreign Minister Andrei Kozyrev said he wanted to end the

crisis in the next few days. ''If Grozny does not use its chance today,

it will be too late tomorrow,'' he said.

Fighting flared in Pervomaiskaya, 15 miles north-west of Grozny, for

the third day running, but died down quickly in the fog. Russian tanks

and artillery pounded the village but there was little response from the

Chechens, witnesses said.

The Russian troops continued a three-pronged advance to try to seal

off Grozny. Moscow has said it will not storm the city of 400,000 but

its patience is wearing thin.

Tass said the fog prevented troops from blockading the town. Yeltsin

hopes a blockade will force the mainly-Muslim region of about one

million people to drop a 1991 declaration of independence.

Grozny looked like a city under siege. Few food shops were trading, a

long queue gathered at the only bakery open, and good fruit was scarce.

Viktor Ilyukhin, who heads the security committee in the State Duma,

Russia's lower House of Parliament, quoted the Defence Ministry as

saying 15 Russians had been killed in fighting so far. Chechen losses

were not known.

Russian military sources said 11 Russian servicemen, captured four

days ago, were still being held captive, six of them in Grozny.--Reuter.