Vietnam has declared a U.S.-based activist group a terrorist organization and warned that any Vietnamese found to be involved with the group would be regarded as co-conspirators and punished.

The government said the California-based Viet Tan, or Vietnam Reform Party, had recruited and trained operatives to use weapons and explosives.

Vietnam has long been sensitive to the activities of Viet Tan, calling the group "reactionaries," but the announcement state television was the first time it had designated it a terrorist organization.