KIEV, Ukraine (AP) _ Police have arrested a suspect in a killing spree that has claimed the lives of as many as 50 people in western Ukraine.

The suspect, a 36-year-old man from central Ukraine, was seized in a police stakeout in a village near the Polish border Sunday night, investigators said Tuesday.

``The main thing is that Ukraine's worst nightmare is over,'' said Alexander Yevashchenko, a senior investigator with Ukraine's Interior Ministry.

Last month, police attributed 39 murders to the killer, who wiped out entire families. But investigators have uncovered evidence that the suspect may have actually killed as many as 50 people. At least 10 of his victims have been children.

On Sunday, police seized what they believe to be one of the murder weapons, a 12-gauge sawed-off shotgun, in the tiny house of the suspect's girlfriend in Yavoriv, a village less than 12 miles from Poland. They also discovered clothes, televisions, car keys and other evidence from the scenes of some of the murders.

The suspect, identified only as Mr. O., is from the Zhytomyr region of central Ukraine and graduated from a local forestry institute. He hasn't registered an official residence since 1988, and has reportedly traveled to Germany several times, investigators said.

The slayings, which began Dec. 30, have terrified Ukrainians, especially in the western village of Bratkovichi, where many of the killings took place.

The village, home to some 1,500 people, has become an armed camp, with police and soldiers on constant patrol and people living behind barred windows. Yevashchenko said the safety measures would continue until the murderer is convicted.

Investigators have described the killings as the work of a maniac with a grudge against families, perhaps driven to seek revenge for his own unhappy childhood. But stolen objects found in the suspect's apartment may indicate he was also motivated by theft, Lt. Gen. Leonid Borodich, first deputy interior minister, told a news conference.

The suspect is not the 40-year-old ex-convict police initially sought, a man named Vladimir Ignatenko and nicknamed ``Baldy.'' Yevashchenko said there was not enough evidence against Ignatenko.