The group of Maoists fired at the Chenpur police station after 1 am. A strong retaliatory action by the police forced them to flee the spot, police said.
However, there was no injury to policemen in the Maoist attack, they said.
Giridih Superintendent of Police A V Homkar said a bomb was found fitted on the railway track between Chebro and Choudharybag halts in Giridih district this morning.
Some trains were held up for some hours at various places for the reason, he said.
Maoists have called the bandh after observing a 'Protest Week' following the killing of some of their top leaders at Chatra on March 28 by their rival, the Trititya Prastuti Committee.