The committee, headed by Federal Security Service chief Nikolai Patrushev, said Tuesday foreign sources had warned the FSB about a possible terrorist plot to attack ground transport and one of the country's subway systems.
"Information provided by our foreign colleagues has not been substantiated for now," said Nikolai Sintsov, a committee spokesman.
But he said the measures taken following the alert had helped reduce the terrorist threat in transport and thanked passenger transport companies and passengers for their vigilance and assistance.
"We have received over 100 phone calls alerting us of suspicious facts. Some of them are still being checked," Sintsov said, adding the enhanced security measures had helped seize 10 kilograms of explosives in the Urals.
The national security service, which did not specify which country issued the warnings, recommended that heads of passenger transport companies take pains to ensure people's security and advised passengers to inform police of anything suspicious.
Anti-terrorism policing was stepped up in the Moscow Metro, and the FSB's regional departments throughout Russia were put on high alert to forestall any attacks.
Security was also reinforced at especially important military and state facilities, natural gas and oil companies. Organized trips of schoolchildren on public transport have been canceled until further notice.
Sintsov said anti-terrorism squads remained on high alert.
Two bomb explosions in Moscow's metro system in 2004 killed a total of 49 people and injured more than 300.
A bomb detonated in a train carriage between the central metro stations Avtozavodskaya and Paveletskaya in February, and in August another went off near the entrance to Rizhskaya station in northern Moscow.
