ANCHORAGE, Alaska (AP) — A rash of unsolved outdoor homicides in Alaska's largest city is putting residents on edge.

Altogether, the deaths of nine people who were killed on Anchorage trails, parks and isolated streets since January remain unsolved — among them three cases involving two victims each.

"It's terrifying," said Jennifer Hazen, a longtime resident who lives near Valley of the Moon Park, where two people were found dead early Sunday, one of them on a park bike trail. Hazen walks in the park regularly, and finds some comfort in knowing the unsolved homicides occurred in the middle of the night when she wouldn't be out there anyway.

"I'm just really shocked about all this happening," said another resident, Yegor Christman as he walked his dog on the bike trail. "I thought I lived in a pretty safe area."

Adding to the feeling of vulnerability, Anchorage has had 25 homicides this year. That's the same number the city had for the entire year in 2015. Even though the number is high, police point out that 1995, with 29 homicides, had the highest numbers in the last two decades.

With 15 homicides since late June, police issued an unusual public advisory this week urging residents to be "extra aware" of their surroundings, noting that crimes often increase at night and early in the morning.

"APD wants to remind our citizens to be cautious when they are out during these hours, especially if they are in isolated areas like our parks, bike trails or unoccupied streets," the police department wrote. "If you plan to be out late at night, make sure you travel with several friends and not alone."

Police Chief Chris Tolley downplayed the significance of the advisory, saying police often remind the public to be safe, sometimes through a text messaging system. Earlier this year, police issued a similar safety alert after a series of car break-ins and thefts, Tolley said. The goal was the same in this week's advisory, to inform the public.

"This is no different," he said. "We want our public to be proactive. So this is really a plea to them in their personal safety."

Three of the victims were found alone. Two of those victims had been shot, according to police, who will not say how the other seven died. They won't say what details have been shared with the families of the victims. Relatives could not immediately be reached for comment Friday.

Police have released few details on any of the cases, saying investigators haven't made any clear connections between the victims. Asked if police believe a serial killer could be on the loose, police spokeswoman Jennifer Castro said police always try to determine if unsolved crimes are related.

The only common denominators found among the victims are that the deaths occurred outdoors, in the early hours and in isolated places such as trails and unoccupied streets.

John McCleary is a longtime volunteer with the city's Trail Watch program, which was started in 2006 after a string of assaults, mostly against women, on local trails. Trail Watch volunteers serve two purposes, to be the eyes for the police department, reporting any problems, and to create safer conditions on 300 miles of trails with such efforts as cutting down vegetation.

But McCleary, the former director of the program for the city, said he's never seen a situation with so many unsolved killings — and he's been connected with city trails since the late 1970s. He says he feels angry and frustrated that people can't enjoy the trails like they could a decade ago.

"This is ... so abnormal," he said. "It doesn't seem like I'm in the same city."

Randall Alcala walks almost daily along the downtown Ship Creek Trail, where two homicide victims were found dead in July. But those deaths, even though unsolved, don't make him feel unsafe.

He just saw a black bear on the trail about a week ago, and is more leery of run-ins with one of the city's hundreds of bears.