Sindh province police chief Hazoor Baksh Junejo said the man suspected of killing local performer Samina Sindhu has been arrested.
Ms Sindhu’s husband Mohammad Ashiq said the party was held by a wealthy landlord to celebrate his son’s birth.
He said one of the guests drunkenly ordered Ms Sindhu to dance before shooting her.
Local TV has aired footage of the shooting, which sparked anger on social media.
Shama Junejo, a human rights activist, tweeted that the singer had to perform due to poverty and that her husband was under pressure to drop the charges.