Greenland was in mourning Thursday after an 8-year-old girl and two women were bludgeoned to death and two men seriously injured in a remote Inuit village.
Flags flew at half staff and two minutes of silence were observed across the giant, but sparsely populated island, where violence of that scale is rare.
A 22-year-old man was arrested on preliminary charges, including three counts of murder and four counts of attempted murder, police said. The attack happened Wednesday in Nutaarmiut, a west coast hamlet with 46 inhabitants, about 560 miles (900 kilometers) north of the Arctic Circle.
The victims were initially believed to have been shot, but police spokesman Claus Risbjerg said Thursday the killer had used blunt instruments, probably hammers, to bludgeon the girl and two women, aged 31 and 75.
Two men, aged 32 and 81, were seriously injured in the attack and flown to Denmark for treatment, Risbjerg said, adding the condition of the 81-year-old man was "very critical."
Greenland, most of which is covered by an ice cap, is a semiautonomous Danish territory.
Another woman and her daughter narrowly escaped the attack, police said, but didn't give details.
Risbjerg said the victims were family related but declined to comment on local reports that the motive could be a family dispute.
"We are still investigating to establish the motive," Risbjerg told The Associated Press.
Premier Kuupik Kleist and parliamentary Speaker Josef Motzfeldt urged the Arctic island's 56,600 inhabitants to "show their respect" by lowering flags and observing two minutes of silence.
Greenland is struggling with social problems including alcoholism and domestic violence, but multiple murders are rare. The latest official figures show nine people were murdered in 2009, while there were 21 attempted murders and 812 violent crimes, including brawls and domestic violence.