Four barrels containing 200 kilograms of explosives were discovered in the capital of Ingushetia, while officials were sifting through rubble of a previous explosion that had resulted in the deaths of four servicemen.
The explosives had been connected to detonators, but had since been neutralized.
“This bomb could have exploded at any minute,” said a FSB source to the RIA Novosti agency.
The Four servicemen died after an explosion as a result of a counterterrorist operation in Ingushetia.
A group of militants was detected during routine passport checks in Nazran and were later trapped in a house in the Tsentr-Kamaz district.
Militants refused to surrender and opened fire.
An additional group of heavily armed servicemen were called to the scene of the shootout.
Under the rubble, according to Russia's First Channel, were found the bodies of three militants.
Latest updates say one of the killed militants is Zeitun Sultanov, who was on an international wanted list for an attact on the city of Nalchik in Kabardino-Balkaria in 2005 in which militants targeted Russian security forces killing more than 100 people, including at least 14 civilians.
He was also linked with the murders of nine hunters in the region in 2007.