For more than six decades it was the social hub of the Soviet elite. A domineering hotel metres away from the walls of the Kremlin, it was the designated posting house of party luminaries, and Stalin liked to celebrate his birthday in its plush restaurant.

But this week it has emerged that the guests of the hotel Moskva were literally sitting on a timebomb. Workmen demolishing the structure found more than a tonne of explosives in its foundations, city police revealed this week.

They said the explosives had probably been planted by the NKVD - the KGB's predecessor - to be detonated if the Nazis took the capital during the second world war.

Police insisted the 58 boxes, each containing 20kg (44lb) of explosives, had not been rigged to a detonator and posed no threat. Sappers cleared the explosive on Monday.

A police spokesman told the state's RIA Novosti news agency: "When German troops neared Moscow in the fall of 1941, the Soviet government ordered the mining of a lot of objects of state and military significance."

The intention was to destroy everything within a 150-metre radius. In 1941 the Soviets hoped that would include senior members of the Third Reich, including Goebbels and his propaganda headquarters, which their intelligence suggested would be set up in the hotel.

Today it includes the parliament, a huge underground shopping centre, the Kremlin's outer walls and another luxury hotel.

Since news of the discovery broke, Muscovites have offered explanations for the cache. Yuri Krotov, who says his father worked in a special division of the NKVD tasked with secretly mining the capital, told the Komsomolskaya Pravda newspaper: "My father was a lieutenant in the Separate Specialised Motorised Shooting Brigade. He told me he was in a group that put explosives beneath two buildings. One was beneath the Moskva hotel and the other beneath [the Soviet foreign minister Vyacheslav] Molotov's office."

The media have since speculated that a second device is beneath a key foreign ministry building used to welcome state visitors.

Mr Krotov said he had been "shocked" to hear about the explosives find at the Moskva. "I was sure it had been taken away," he said. He added that as many as half of his father's unit had died in counter-espionage work during the war, leaving few people to remind the authorities to remove the cache.

Yuri Zhukov, a senior historian at the Russian Academy of Science, said: "More than a hundred buildings were mined, including the Kremlin." He said he thought the explosives had been accidentally left beneath the Moskva, but removed from other buildings. The idea to mine buildings, he said, had come from Stalin's feared security chief Lavrenty Beria and had been approved by Stalin.

The Moskva hotel was one of the capital's main landmarks until the mayor of Moscow, Yuri Luzhkov, began demolishing it in 2002. Its guests have included Robert De Niro, Boris Yeltsin and Guy Burgess, the Soviet spy in the Foreign Office who was a resident there from defection in 1951 to his death in 1963. Marshall Zhukov rested in one of its 2,000 rooms on his victorious return from the front in 1945, and Yuri Gagarin stayed there after his first space flight.