A 7-year-old suburban Maryland boy playing with a friend in a creek near a community swimming pool in Aspen Hill yesterday was attacked without warning by two older youths who beat him and repeatedly slashed him with knives, Montgomery County police reported.

The injured boy, whose name was not released, was later found lying unconscious face-down in a foot of water in the creek where the assault occurred.

He was flown by Maryland State Police helicopter to Children's Hospital, where he was undergoing surgery and listed in critical condition last night with a fractured skull and multiple lacerations to his face, a hospital spokeswoman said.

Police, who said the 5 p.m. attack occurred without provocation and with no apparent motive, were searching for two suspects believed to be 14 to 20 years old. A 10-year-old boy who was playing in the creek at the time of the attack escaped injury, police said.

Police said they were puzzled by the assault near Burlwood Drive and Connecticut Avenue in Aspen Hill, saying it was without parallel in the shaded residential neighborhood there. Authorities were still trying to determine precisely how the attack occurred.

According to Montgomery County police spokesman Sgt. Harry Geehreng, the 7-year-old and the 10-year-old, both of whom live a short distance away, were playing in Turkey Branch Creek, a shallow body of water that runs through a deep gully between Burlwood Drive and Turkey Branch Parkway.

The boys were standing barefoot in the creek skipping stones across the water, Geehreng said, when they were suddenly surprised by the older youths, who were dressed in shorts and carrying beach towels. The older youths produced knives and attacked the 7-year-old while his 10-year-old playmate ran away.

One detective said it is still unknown whether the assailants followed the boys into the creek, or whether they encountered each other there by chance. Several steep paths lead from the two roadways through thick underbrush into the area.

He said the older youths probably approached from the parkway and that police were investigating the possibility that they had come from the Aspen Hill swimming pool.

The 10-year-old who escaped ran about 25 feet up the embankment to Burlwood Drive, police said, where he found the father of the injured boy and told him what had happened. The man, whom police declined to identify, accompanied the boy back to the creek, where they found the 7-year-old face-down in the water.

A neighbor, Nick Scholz, said he ran to the creek to help the father and that the 7-year-old, "severely beaten" and "bleeding from the eyes, the ears and alongside his head," was carried back to his house where the men called authorities.

Scholz said he had been trying for some time to get county officials to clean up the area near the creek, saying it was used as "a garbage dump" and was strewn with debris.

Geehreng said that in addition to being stabbed and beaten, the injured boy might also have been struck with stones.