Russian authorities have canceled the state of alert announced earlier this week in response to an unspecified terrorist threat.

State security officials say they returned security forces to normal duty Friday.

Tuesday, Russia's Federal Security Service said it had received information about a possible attack on ground transportation or in a subway. An official said the information was received from "foreign partners." It is not clear what country or entity provided the information that led to the alert.

Authorities Wednesday said they had no evidence to confirm the reported terrorist threat.

Moscow has been the target of many attacks on civilians in recent years, including a 2002 theater siege that killed at least 129 people, and an attack on a school in the town of Beslan in 2004 that left more than 300 people dead.

Some information for this report was provided by Reuters.