Calgary police have charged three men with conspiracy to commit murder in what they say is a rivalry between local gangs.

The trio hatched a plan to kill a man who is currently serving a lengthy prison sentence for an unrelated shooting, police said.

The men were arrested Friday. Two of the accused were arrested in Calgary and the third in Saskatoon, police said. 

During the search of a southwest Calgary home police also seized drugs, cash and weapons.

A woman not linked to the alleged conspiracy was also arrested during that raid for drugs and weapons offences.

The investigation lasted more than six months, police said.