The dawn-to-dusk Bihar bandh called by the Vishwa Hindu Parishad began on Tuesday morning.
The outfit is protesting against the recent action of the state government to deport its leaders Praveen Togadia and Giriraj Kishore on their arrival in Patna.
Vehicular traffic movement was thin while shops in residential areas in Patna opened as usual, official sources said.
An alert has been sounded across the state and patrolling has also been intensified in view of the bandh, they said.
All police stations are on maximum alert while special attention is being given to protect vital installations, including properties of the state government.