Patna, Sep 17 - Bihar's ruling Janata Dal-United (JD-U) has taken a clear lead on five seats in the by-elections to 18 assembly constituencies in the state, counting for which was underway Thursday.

According to early trends, the opposition Rashtriya Janata Dal was leading on three seats and its ally Lok Janshakti Party was ahead in two constituencies.

The by-elections for 18 seats were held in two phases in the state. In the first phase, polls were conducted in seven constituencies Sep 10, while the rest went to polls Sep 15.

The elections were necessitated to fill up the seats mostly vacated by sitting legislators to contest the April-May Lok Sabha polls.

The vote is being seen as a mini-referendum for the Nitish Kumar government ahead of state assembly polls slated for next year.

Chief Minister Nitish Kumar, JD-U national president Sharad Yadav, Rashtriya Janata Dal (RJD) chief Lalu Prasad, Lok Janshakti Party chief Ram Vilas Paswan and several central ministers and Congress leaders campaigned for the by-polls.