Singh was a member of Bihar Legislative Council and the deputy leader of the party in the upper house of the Assembly.
Chief Minister Nitish Kumar, expressing profound grief over the death of the leader, announced state mourning tomorrow in respect of Singh. Singh was Parliamentary Affairs minister in previous state government led by Kumar.
Kumar said he was a "very friendly" person and had a clean image in state politics spanning over five decades.
State Assembly Speaker Uday Narain Chaudhury and Bihar JD-U president Basisht Narayan Singh also mourned the death of Singh, one of the senior most leaders of Bihar.