Thirteen persons were dead and one seriously injured today after they were gunned down execution-style at the Wah Mee club, a private gambling establishment in this city's Chinatown section.

Two men in their early 20s were arrested in connection with the shootings, which rank as one of the nation's worst single-day mass slayings.

The victims, 13 men and one woman, were all Asian and ranged in age from the 20s to 70s. They had been tied and then shot in the head--some more than once.

One man, found in an alley outside the club, was in serious condition at a local hospital tonight with a bullet wound in his head.

Seattle police said robbery appeared to be the motive in the shootings. At a conference this afternoon, they said they believed the killings were not connected to any organized crime or gambling activity.

Police found only one wallet among the victims in the club, and no money was seen.

Most of the victims were found in the club's gaming room. One, who was not bound, was discovered in the club's office.

The suspects, Benjamin Ng, 20, and Kwan Mak, 22, were arrested within hours of the killings. Ng was arrested at home and Mak turned himself in, police said.

Police, who were still seeking a third suspect, said another person was questioned and released.

The two suspects in custody, both Chinese, were being held without bail. A hearing is scheduled for Tuesday.

Police learned of the killings after a passer-by found the lone survivor, Wai Chin, 62, staggering in the alley after apparently freeing himself from his bonds.

Officers pried open the doors to the club and found the others on the blood-soaked floor. "The bodies were just strewn on the floor," said Seattle police spokesman Gary Flynn.

Police Capt. Mike Slessman said the victims, most of whom were in the restaurant business, had been playing "paykyo," a gambling game using dominoes, with rules similar to blackjack. The game is popular among the clubs in Chinatown because it involves many players and usually much money.

While the sheer number of the killings stunned members of Seattle's Asian community, gambling is not new to Chinatown, and neither is violence.

Most recently, three murders in 1977 were linked with gambling. Two persons were gunned down at Seattle's China Gate Restaurant in front of other patrons, and an 87-year-old man was fatally shot in a gambling club.

The Associated Press reported today that Police Chief Patrick Fitzsimons called gambling clubs a chronic problem in Chinatown.

". . . There are chronic problems that we deal with as well as we can when the law allows," he said. ". . . If we have opportunity to take legal enforcement action, we do it. But we always have to have the evidence or the probable cause we need to get search warrants," he said.

The Wah Mee is the oldest of the gambling clubs in Chinatown, a place especially popular with many members of the Asian community during the 1950s when, under Seattle's blue laws, nightclubs were legally required to close before midnight. The club's patrons are screened through a one-way mirror before being allowed to enter. Police last raided the Wah Mee in 1972.

Today the club, located in an alley behind a grocery story, was chained and padlocked by Seattle police.