A Janata Dal Rashtravadi party candidate and one of his supporters were shot dead during their poll campaign in Bihar's Sheohar, while the suspected attacker was also attacked, the police said on Sunday.
Shri Narayan Singh, 45, was killed on Saturday evening while campaigning at the Hathsar village in the Puyanhiya police station area, they said Narayan Singh himself had a criminal record and over three dozen cases registered against him, they said.
Senior police official Santosh Singh linked the killing to a "gang war".
Sheohar's police official Rakesh Kumar said Narayan Singh was shot in his chest. He was rushed to the Sheohar Sadar Hospital from where he was referred to another facility, but he died on the way, the police said.
Shri Narayan Singh was campaigning when the attack happened, senior police official Mr Singh said.
The suspected attacker was in the crowd walking with the candidate and shot at him, he said.
One of the candidate's supporters was also injured and he later died, he added. The attacker was then beaten to death by the mob, the officer said.
The Sheohar seat has 15 candidates in the fray, including five independents.
The RJD, the JDU and the LJP have fielded their candidates from the seat. The BSP is also contesting.
Police said security has been tightened in the area and paramilitary personnel deployed.
Trihut Range Inspector General of Police Ganesh Kumar visited the spot.
The police said Shri Narayan Singh's last rite has not been conducted yet.
The constituency goes to poll in the second phase on November 3. The Janata Dal Rashtravadi is a registered party.