Russian authorities have placed security forces on high alert after receiving information of plans for a possible terrorist attack on the country's transportation system.
Officials at the Federal Security Service in Moscow say the information, received from what they termed "foreign partners," involves a possible attack on ground transport or in a subway.
They say Federal Security Chief Nikolai Patrushev ordered the alert and called for stepped-up measures to prevent any attack. The officials gave no details on the nature of the threat or measures taken.
It remains unclear what country provided the information that led to the alert. Russia cooperates in the fight against terrorism with countries around the world, including the United States.
Some information for this report was provided by AP.