Two double murders, all within a span of 36 hours, have left residents of this industrial and commercial hub of Punjab shocked.

The recovery of the body of a deputy superintendent of police (DSP), Balraj Singh Gill, and an unidentified woman -- both of whom were brutally killed -- from a farmhouse near here on Thursday morning has put the Punjab Police in a spot.

Investigating officers on Friday said they were not ruling out revenge killing and the links between the DSP and the woman were being investigated.

Gill's blood stained body was found on the sofa in the farmhouse, located on Hambran road, with his head hanging as his neck had been sliced. His body had several other injuries inflicted by sharp-edged weapons.

The woman, identified as Monica Kapila, 35, a resident of Model Town locality here, was also killed with sharp-edged weapons. Police on Friday said they were investigating the links between the two, including the possibility of an extra-marital affair.

Her body, which was not identified on Thursday and not even claimed by anyone, was identified on Friday by her trader husband.

"We are investigating how the officer and Monica got together at the farmhouse. No arrests have been made so far," investigating officer Ram Pal said.

Gill, who was awarded the President's police medal in 2010, had led the parade during Republic Day celebrations at Moga town, where he was posted as DSP. He was a keen sports and adventure enthusiast.

Even though the police have not made any arrests, they have recovered the car in which the DSP had left his house on Wednesday evening and did not return. His family informed the police when he did not return for several hours. His body was recovered from the farmhouse after the police got a call from someone.

Police here said that the car, belonging to a friend of Gill, was found near Nurpur Bedi area in Ropar district, 100 km from here.

Assistant Commissioner of Police Gurpreet Singh said the DSP's murder seemed to be a conspiracy. He said the officer was attacked as soon as he entered the farmhouse.

He said the DSP put up some resistance against his assailants, who could be three-four in number, but was pinned down by them and then murdered.

"The DSP was not carrying his service weapon at the time of the incident. He did not take his security personnel either," an investigating officer said.

The killing was preceded by another double murder which police say is a case of honour killing, in which Barjinder Singh, the son of a Congress leader, shot dead his 25-year-old sister and her lover when he found them in a room inside their house in Hambran village, 20 km from Ludhiana.

Barjinder, who is now in police custody, killed his sister Navdeep Kaur and her boyfriend Harpeet Singh, with a revolver from point blank range after he found them together in a room in their (Barjinder and Navdeep's) house in the wee hours of Tuesday, police said.

The accused, who surrendered to the police just hours after committing the double murder, told the police later that Harpreet had entered their house secretly past midnight after talking to his sister.

Police said that Barjinder first killed Harpreet and later shot dead his sister on the temple.