Accused Craigslist killer Philip Markoff reportedly tried to hang himself in his jail cell with shoelaces and was placed on suicide watch Thursday.

Correction officers found “shoelace marks” around the 22-year-old med student’s neck, law enforcement sources told ABC News.

He was quickly moved to a segregated unit at Boston’s Nashua St. jail so officers can keep a closer watch on him.

Markoff is being held without bail on murder, kidnapping and robbery charges in the slaying of Manhattan masseuse Julissa Brisman and the stickup of hooker Trisha Leffler.

The preppy upstate New York native – who was attending Boston University medical school – allegedly lured his prey over Craigslist.

Police said he was using the robberies to finance a gambling addiction and that he killed Brisman – with a gun he stashed in a hollowed out copy of Gray’s Anatomy – when she fought back.

He was arrested Monday on the way to Foxwoods casino in Connecticut with his fiancee, Megan McAllister.

She is standing by him despite mounting evidence of his guilt – including panties from the victims found in the Boston-area apartment they shared.

“She’s still confident in Phil,” her father, Jim McAllister, said outside the family’s home in Little Silver, N.J.

“We’re saying a lot of prayers.”

Asked whether McAllister had any idea her future husband might be involved in criminal activity, her father answered, “Absolutely none.”

Meanwhile, friends and relatives of Brisman gathered in Washington Heights for the second day of a wake. She will be buried Friday, on what would have been her 26th birthday.