BELLINGHAM, Mass. (AP) _ Two young men were arrested Tuesday on charges of abducting a 15-year-old girl at gunpoint from her bedroom while her parents slept. Police also accused them of terrorizing two other teens in their homes over the past three days.

In the latest assault, Wendy DeCasse was bound, gagged and forced from her home early Monday. She apparently was raped during a day in captivity then released early Tuesday, police said.

Police in this rural area 30 miles southwest of Boston, near the Rhode Island state line, said they had stopped the two suspects, both 18, for driving with a noisy muffler, then saw a .22-caliber rifle and rolls of tape on the back seat. They took the pair in for questioning about the gun, and learned that Miss DeCasse had just returned home.

''My daughter's home, she's safe,'' Caroline DeCasse said in a telephone interview. She refused to discuss the matter further.

Joseph L. Allen Jr. of Milford and Richard C.A. Babcock Jr. of Milford and Woonstocket, R.I., were taken to Milford District Court for arraignment on kidnapping, rape and other charges.

Allen's father, Joseph L. Allen Sr., is serving two concurrent life terms in a state prison for the September 1982 murders of his estranged wife and her lover, according to police and news accounts at the time. After the slayings, he shot himself in the head in an unsuccessful suicide attempt.

The next day, the younger Allen, then 15, found his critically injured father and the bodies of his mother and her lover. He later testified at the murder trial of his father, who suffered brain damage in the shooting.

Tuesday afternoon, District Judge Francis J. Larkin ordered Babcock and Allen held at a state mental hospital for 20 days to determine their competency to face the charges after a court psychiatrist examined them and recommended further evaluation.

''I feel that both of these young men have significant psychological problems,'' Dr. James Robison told the judge.

The charges against Allen and Babcock included two counts of armed assault in a dwelling, the result of an incident Saturday in nearby Mendon and one Sunday at a house near the DeCasses' home.

In those incidents, according to court records, the pair allegedly held young residents of the homes captive at gunpoint.

Mrs. DeCasse and her husband, Nelson, told police they had been awakened early Monday by their screaming 10-year-old daughter Heidi. She said two men dressed in Army fatigues and brandishing weapons had entered the bedroom she shared with her sister, bound and gagged Wendy with tape and carried her from the house in her nightgown and bathrobe.

The DeCasses at first tried to calm Heidi, believing she had suffered a nightmare, but her insistence led to the discovery that Wendy was missing. Outside, police found telephone lines leading to the house had been cut.

In two previous incidents, according to court records, the suspects held young residents of homes captive at gunpoint.

Late Sunday, Allen and Babcock allegedly invaded a home several blocks from the DeCasses', holding a 17-year-old boy captive with a handgun until interrupted, police said. They refused to provide further details of the case.

The other incident that prompted filing of armed assault charges was the foiled abduction Saturday of another Blackstone Valley Regional Vocational and Technical High School girl from her home, police said.

In that case, an intruder broke into a house about 12:45 a.m. and held a gun to a 16-year-old girl's head, said Mendon Police Lt. Dennis Grady. When her mother returned home, the girl shouted a warning. As her mother returned to her car, the girl jumped out a window and the mother and daughter then sped from the house, he said.

John LeBrun, principal of the 900-pupil Blackstone Valley Regional school, said students were relieved when he announced that Wendy had returned home safely. Students from her neighborhood had been upset by the kidnapping but were not afraid, he said.

''We've got a pretty level-headed group of students down in this part of the state,'' he said. ''They don't panic too easily.''