The Patna police has launched a search operation to arrest Patna Mayor Krishna Murari Yadav and three others following non-bailable warrants of arrest issued against them in connection with the killing of Rashtriya Janata Dal leader and Patna Water Board Chairman Ashok Yadav.

Senior Superintendent of Police N H Khan said on Saturday that the police raided some places in Patna to arrest the Patna mayor and the others.

"The police had intensified raids to nab them soon and we have got a vital clue in the case," said Khan.

• Senior RJD leader killed in bomb attack in Patna

Chief Judicial Magistrate R P Chaubey issued warrants against the mayor, his son-in-law and Zilla Parishad Chairman Sanjay Yadav and the chief engineer of Water Board Ravindra Kumar on the plea of the district police on Friday.

Early this week, a first information report had been registered against Mayor Yadav, his son-in-law Sanjay Kumar, District Board Chairman Ravindra Yadav, and the chief engineer of the Water Board on the basis of a statement by Ashok Yadav's brother Ganesh Yadav.

Ashok Yadav was killed and five ward councillors of the Patna Municipal Corporation were also injured in a bomb attack in Patna on Monday.

Yadav is the second RJD leader to be killed in Patna after President's rule was imposed in the state in March 2005. The news of the attack on Yadav and his death sent shockwaves in several parts of his stronghold.

The RJD has demanded a Central Bureau of Investigation probe into the killing of Ashok Yadav.