An 8-year-old District girl attending a weekend birthday celebration in Hyattsville was struck in the head by a rock and seriously wounded when a fight broke out after an informal teen-age soccer game, Prince George's County police reported yesterday.

They said a 15-year-old Northeast Washington youth, whose name was not released, was arrested and charged with two counts of assault with intent to maim in the incident after he turned himself into police yesterday evening.

Judy Arias of 1440 Columbia Rd. NW was listed in serious condition last night at Children's Hospital with a depressed skull fracture, according to hospital officials.

Police said the incident occurred shortly after 8 p.m. Sunday while Judy and her family were visiting relatives at 5008 54th Ave., Hyattsville, to celebrate the eighth birthday of her cousin, David Arias.

Members of Judy's family and her cousin's family were playing soccer in the street against another neighborhood group when fighting broke out, police and witnesses said.

About 20 people began fighting, including soccer players and adults, police said, and during the altercation one hurled a rock at Judy's father, Juan, who ducked. The rock struck the girl.

In an interview yesterday, Juan Arias said the family gathering was held at the home of his brother, Enrique. Juan Arias said he was in the basement of the house when another of Enrique's sons, Ricardo, 14, came in bleeding from the face.

Juan Arias said he went into the front yard of the house, where a large group of youths and adults had gathered, many of whom were shouting loudly.

Some of them had come from a cookout about three blocks away, according to police.

Juan Arias and Prince George's police detective Robert Young said the neighbors began fighting because of the soccer game and, Young added, "one thing led to another."

Arias said a youth threw a rock that hit him in the shoulder, and when the youth threw a second rock at him, he ducked. That rock hit Judy Arias, who was standing nearby.

"After that, I leaped over the fence and grabbed the youth ," Arias said, at which point police arrived.

Judy was taken to Prince George's General Hospital, where she was initially listed in "extremely critical" condition and then airlifted to Children's Hospital.

A neighbor, who said she was eating dinner during the melee, said she could hear loud racial epithets coming from the fracas, which, according to police, involved groups of Hispanics and blacks.

"There was screaming . . . . I never heard such carrying on," said the neighbor, who asked not to be identified.

"It was the parents who caused it because it would have been just a kids' fight," said Edwin Valasquez, who lives next door to the house where the incident took place. Valasquez said he arrived as the incident was clearing up, but said he spoke with several of the participants afterward.

"They came here," Arias said of the youths and adults who came from several blocks away. "We were at home eating cake. We talked. We were playing."

Arias, who is employed in the District as a maintenance man at a warehouse, said he, his brother and other members of the family moved to Washington in 1975 to escape the overty of their native Ecuador.

"It's different here," Arias said. "There are very many poor people where I come from."

His wife, Petita, is currently in Ecuador visiting her mother, who is ill, and she has not been informed of her daughter's injury, Arias said.

Judy was to have begun third grade today at Bancroft Elementary School, according to her aunt, Patricia Arias.