Police arrested an Olney man on murder charges after he allegedly shot another man to death early yesterday during an argument.

Sophal Siv, 45, of Marshall Street near Duncannon Avenue, allegedly shot Hai Luu, 39, of Cherry Hill, N.J., just before 3 a.m. on Old York Road near Rockland in Logan, police said. Luu died about a half hour later at Albert Einstein Medical Center. Siv was arrested at the scene.

Police continue seeking suspects in two other unrelated weekend homicides:

* Someone shot Rashul Isaacs, 28, of 18th Street near Morris in Point Breeze, in the neck, arm and legs just before 3 a.m. yesterday at 35th and Wharton streets. Isaacs died 15 minutes later at the Hospital of the University of Pennsylvania. The motive remains unknown, and police have no suspects.

*  Nearly three hours later, someone stabbed Luionel Perez, 21, of 6th Street near Lehigh Avenue in Fairhill, in the neck on Hasbrook Avenue near Benner in Crescentville. Paramedics declared Perez dead on the scene. at 5:52 a.m. The motive remains unknown, and police reported no suspects.

Tipsters can call homicide detectives at (215) 686-3334 or -3335.