Khalid Alladita, a resident of Chechawatni, located 250 km from Lahore, served juice to his mother, Irshad Bibi, 55, and his sisters Nazia, Shazia, Faiza and Sajida, aged between 18 and 28.
The juice was laced with some substance and the women fell unconscious after drinking it.
Alladita then stabbed the women to death, police said.
Alladita told police officials that he killed his mother and sisters to protect his family's honour.
"Two of my sisters had relations with men of our locality. My mother and the other sisters did not stop them from seeing these men," he was quoted as saying by police.
Local residents told police that Alladita was a drug addict and he often quarrelled with his mother and sisters for not giving him money.
Lahore: In a gruesome case of honour killing, a man in Pakistan's Punjab province allegedly killed his mother and four young sisters on Thursday after accusing two of his siblings of having relations with men in their neighbourhood.
First Published: Thursday, August 30, 2012, 22:50