In a letter to his Pakistani counterpart Sartaj Aziz, Russian foreign minister Igor Ivanov demanded that Islamabad take concrete and tangible steps to check cross-border terrorism, the sources told PTI.

Ivanov reportedly expressed Moscow's dissatisfaction over Islamabad's repeated denials of its involvement in sending mercenaries and terrorists to Chechnya.

Acting on the orders of President Boris Yeltsin, he cautioned Aziz that encouragement of such subversive and terrorist activities could pose a threat to the existence of the existing regime in his country.

Meanwhile, Russian daily Izvestia reported that Laden, who had reportedly dispatched 70 Arab mercenaries to Chechnya, plans to send over 50 moreguerrillas from his Peshawar-based centre Bin-al-Ansaradion.

The daily, quoting intelligence sources, said that these militants, holding business passports, would fly from Islamabad to Turkey and then proceed to Azerbaijan to sneak into the neighbouring Chechnya.

Izvestia said it had the evidence that Pakistani, Saudi, Afghani and even Burmese mercenaries were among the Chechen militants fighting in Dagestan.