GROZNY -- Chechen authorities threatened Monday to execute 58 Russians, including alleged army officers and soldiers, unless Moscow admits that its troops were involved in an unsuccessful assault Saturday on the breakaway region's capital.


"If by 1800 hours Tuesday, Russia does not admit that its troops stormed Grozny," a government spokesman said, "the prisoners will be treated according to the republic's wartime regulations."


Those regulations mean that the prisoners would be executed, the spokesman said.


However Chechen President Dzhokhar Dudayev later toned down the ultimatum, saying the soldiers would be judged according to "international law."


Dudayev's war council had issued the threat on Sunday night.


"If Russia does not recognize these soldiers as prisoners of war they will be tried by Islamic law. I will not lift a finger to stop this process," Dudayev said late Sunday. "There is only one sentence for mercenaries."


In Moscow, Itar-Tass news agency said Monday that President Boris Yeltsin had called an extraordinary meeting of the Security Council to discuss the situation, while Defense Minister Pavel Grachev denied that any regular Russian army troops had been involved in fighting in Chechnya.


State Duma speaker Ivan Rybkin said the Security Council would meet on Monday evening, and reiterated denials of Russian involvment.


"It is impossible to speak of Russian inteference in the Chechn conflict," he he said, according to Itar-Tass. "Chechnya is party of Russia." (See analysis, Page 4.)


A spokesman for the Chechen state security council said about 200 opposition fighters were captured Saturday, when they attempted to take the city by force using heavy artillery and tanks. He said 58 of the prisoners were Russians.


Interfax quoted Chechen officials as saying more than 300 opposition fighters were killed in Saturday's battle with more that 30 armored vehicles and tanks destroyed and 12 captured. These figures could not be independently confirmed.


A crowd of about 500 people turned up in the central Freedom Square Monday afternoon in the winter's first snow storm after the government announced it would march the prisoners for public viewing.


Heavily armed Chechen soldiers had to hold the crowd back next to the presidential palace after authorities decided against the public display.


One of the soldiers, Major Molvadi Alkhanov, said he believed the prisoners should be executed, regardless of their nationality.


"If anyone comes to fight against our state, whether he's Chechen, Russian or any other nationality, we should deal with them the Moslem way, with Islamic law," he said. "We should shoot them."


Chechen officials Sunday showed reporters two of the Russian fighters they said had been captured during the abortive assault.


Andrei Chasov, a 21-year-old conscript from Moscow, said he had been sent to Chechnya without being told why.


Nikolai Klimenkov, a 38-year-old tank mechanic, said he had been promised five million rubles ($1,600).


Grachev said mercenaries were fighting on both sides of the Chechen conflict, but that no regular Russian army troops were involved.


"A great number of mercenaries from Afghanistan, the Baltics, and other states, including Russia, are fighting for Dudayev," news agencies quoted Grachev as saying. He did not deny that Russian mercenaries were also fighting alongside the opposition, Itar-Tass and Interfax said.


But, Grachev said, there was no Russian army involvement in the fighting. If the army had been involved, he said: "one paratroop regiment might have solved all questions in two hours."


Chechnya, a mostly Muslim area of 1.2 million in the Caucasus Mountains, declared independence in 1991. Dudayev loyalists say Moscow is providing the opposition with weapons and troops to oust the former Soviet air force general and bring Chechnya back to the Kremlin fold.


Grozny was quiet Monday. Heavy fog may have prevented air operations by the opposition.


Interfax quoted an opposition leader, former head of the Russian parliament Ruslan Khasbulatov, as urging Grozny residents to evacuate their children from the capital, which his forces planned to bomb.


Eyewitnesses saw columns of military lorries carrying ammunition concentrating in Russia near Chechen borders.


Dudayev has threatened to retaliate for what he said was Russian participation in the latest fighting. His forces would "wipe from the map" villages serving as bases for opposition.


(AP, Reuters)