Russian news agency had reported a "strong explosion" in Dagestan's capital Makhachkala Wednesday, saying a shell had explosed in a private house.

The Russian dailies Kommersant and Gazeta, however, quoted police officials in Makhachkala saying that an anti-tank guided missile had broken through the wall of the house and landed in a bedroom without exploding.

Experts quoted by the newspapers said investigators had then found a metal tube, the missile's outer shell, in a courtyard 70 metres away from where the missile had landed.

According to the experts, a malfunction that occurred when the missile separated from its outer shell had caused the missile to steer away from its target.

Police and FSB (former KGB, Russia's secret services) officials discovered two other similar missiles and a missile-launcher pointing towards the building complex, which hosts the local government, the interior ministry and the FSB headquarters, the dailies said.

Witnesses were also reported to have seen two people with bloodied hands leave the house shortly after the missile was launched.

On Thursday, a vehicle carrying an explosive device containing 400 grammes of TNT was found in Makhachkala in proximity of the building from which the anti-tank missile was launched, the ITAR-TASS news agency said.

The bomb was defused, the agency added.

Russian police have been on high alert after more than 400 people died in a series of recent terror attacks blamed on Chechen rebels, including the downing of two commercial planes and a three-day school siege that ended in the deaths of 339 adults and children.

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