The Special Task Force (SIT), formed to investigate the murder of Congress councillor Tapan Kandu in West Bengal's Purulia district, on Saturday arrested the politician's brother and a contract killer, who was hired to carry out the killing, a senior officer said.

SIT sleuths picked them up acting on the inputs provided by Kandu's arrested nephew, the son of the accused brother.

So far, five people were arrested in connection with the killing of Kandu, the councillor of Jhalda Municipality, who was shot dead on March 13 in that town.

"The murder was an act of personal vengeance. There has been a dispute between the two brothers. Three to four years back, the arrested brother had attempted to kill Tapan Kandu but failed," the IPS officer told PTI.

The brother's vengeance grew stronger after his son, a Trinamool Congress leader, lost the municipal election to Kandu, he said.

The "contract killer" is a resident of Bihar and he was approached, on behalf of the brother, by the person who was arrested by the SIT from Giridih on Friday, he said.

The police officer said that the sleuths are trying to find out whether the arrested "contract killer" alone murdered Kandu or he was aided by anyone else.

Kandu's wife has filed a case in the Calcutta High Court seeking a CBI probe into her husband's killing and she stuck to her demand.

On Saturday, she also demanded the arrest of a police officer who allegedly pressured Kandu to join the TMC.