GAINESVILLE, FLA., AUG. 29 -- A terrified college community banded together today through prayer vigils, public rallies and phone calls home as police continued to search for what they call a serial killer wanted in the slayings of five students here since last weekend.

Police agreed on a single, chilling piece of information today, acknowledging for the first time that the first three victims were brutally stabbed over the weekend. They would not describe the murder weapon.

The bodies of Christina P. Powell, 17, and her roommate, Sonya Larson, 18, both University of Florida freshmen, were discovered Sunday. Christa L. Hoyt, 18, a chemistry honors student at nearby Santa Fe Community College, was found dead in her southwest Gainesville apartment early Monday.

Two Florida graduate students, Manuel Taboada and Tracy Paules, both 23, were found dead Tuesday in the apartment they shared at the Gatorwood Apartments near the campus.

Police did not release details of autopsies on the most recent victims and refused to confirm several published reports about the manner in which the victims died, including one that Hoyt was sliced open from pelvis to chest and decapitated.

Police Chief Wayland Clifton called the killer "shrewd" and "methodical" and said "police instinct" leads him to believe that the perpetrator is a single man who may have known his victims and is still in the Gainesville area.

The FBI and state law enforcement officials have joined in the investigation. Two psychologists, including John Douglas, an FBI official who worked on the notorious case of executed serial murder Ted Bundy, have been been brought here to draw up psychological profiles of the assailant.

But police have hesitated to release further details about the crimes, and rumors surface almost hourly about new victims and suspects. "We don't want to agitate this individual to commit any further crimes," Clifton said.

The chief added, however, that he is "very worried" that the killer will strike again.

Similar concerns are gradually emptying the sprawling Florida campus, leaving behind mute evidence of students' fears. Outside the Gatorwood Apartments, a group of Guardian Angels from Tampa set up an outpost in a van. Across from the campus's main entrance, students have tied a length of yellow ribbon around the massive trunk of an oak tree in front of a fraternity house.

Many students, however, have responded in grim fashion. Sporting goods stores have reported a run on chemical mace and guns.

"To tell you the truth, I feel unsafe," said Alaadin Bukhari, an engineering graduate student from Syria who expressed concern that his family has heard of the murders on Cable News Network. "I don't have a gun, but I'm planning to buy a small pistol tonight."

The rush of gun purchases led the North Central Florida Sportsmen's Association to advertise one-hour gun-safety classes for new owners of firearms.

The city, normally an easygoing academic center peopled by casual strollers and teenagers on bicycles, seemed to hold its collective breath today.

Many students, whose classes began Monday, took advantage of the university's promise to withhold academic penalties and left early for the Labor Day weekend. Others doubled and tripled up with friends or in university dormitories and other facilities made available for students living off campus.

Charlie Green, 23, a graduate student from Fort Myers, Fla., said he is going home Thursday. He and his roommate, who are spending nights at their fraternity, plan to have a security system installed in their off-campus apartment.

Like many male students, they said they were shaken by the killing of Taboada at a time when officials had begun to speculate that the killer was targeting petite brunette women.

"Today's been real weird," Green said. "Everybody expected to hear about more bodies."

The local chapter of the National Organization for Women, terming the murders "hate crimes against women," held a rally downtown this evening to mourn the victims and left a wreath in their memory on the plaza in front of the courthouse.

Police and a local radio station that has turned its contest phone lines over to calls from anxious parents report receiving thousands of phone calls. These included people fielding tips about suspicious persons, offers of help from local businesses and expressions of concern from those outside the area who have been able to penetrate clogged long-distance circuits.

Kathy Fain, a counselor from a local psychiatric hospital, said many of those who have asked her help simply want to talk out their fears.

"We tell them to follow safety precautions and use alternative housing," she said. "It's not only students but also single parents with small children who want to know what to do."

At the Florida campus, the student services office, which normally closes at 4:30 p.m., remained open an extra five hours tonight.

"We've just been swamped with calls, as you can imagine, from parents, students, grandparents, brothers, sisters," said James E. Scott, dean of student services.

Scott said daytime classes continued to draw fair attendance today but said night-class attendance probably would be sparse. Officials have decided to keep the university open but have rolled back deadlines for dropping classes until next week and are granting liberal make-up opportunities for students who no longer feel safe in Gainesville.

"This is a very traditional campus," Scott said. "The apartments are close by. The students are very open and friendly. They're always thinking the best, unfortunately."