Over 51 per cent polling has been reported in the fourth phase of assembly elections in Bihar today. Speaking to reporters in New Delhi, Deputy Election Commissioner Vinod Zutshi said the polling was peaceful barring a few minor incidents. Over 46 per cent polling was reported in the bye-election to the Banka Lok Sabha seat. Besides other tight security measures, Mr Zutshi said, four helicopters were also pressed into air surveillance. He said a case has been registered against RJD leader Lalu Prasad for violating the norms of Election Commission.