The National Hockey League has fined the Washington Capitals $7,000 for irregularities in the signing of Finnish forward Mikko Leinonen, NHL President John Ziegler announced yesterday.

The fine is the highest in recent memory by the league. The public announcement also was somewhat unusual; the NHL conducts most actions of that sort in secrecy.

A league spokesman admitted that the fine seemed unusually high and could not recall any others of such magnitude. However, he noted that the bylaws provided for fining clubs from $3,000 to $5,000 for bench-clearing brawls and up to $10,000 for other violations.

The Capitals, while acknowledging that they had made a procedural error, protested the extent of the punishment and formally appealed it to the NHL board of governors.

"Obviously, there was a mistake made. However, the Washington Capitals do not agree to the NHL's position as to the severity of the decision and will appeal the decision to the NHL board of governors," said General Manager David Poile.

Poile signed Leinonen, who formerly played with the New York Rangers, on March 10. That was two days before the date for the finalization of NHL rosters. However, Leinonen continued to participate in playoffs in Finland and did not arrive here until Friday.

According to the NHL bylaws, if Leinonen became Washington property on March 10, he would have had to be placed on waivers in order to play anywhere else after that date.

Ziegler, in a statement released just before he left his New York office yesterday, said, "Even though I have concluded that this was not an intentional attempt to violate the NHL bylaws, nevertheless it is clear that what was done by the player and the club was a serious disregard for our rules."

In addition to the $7,000 fine, Ziegler ruled that Leinonen could not participate in the Capitals' first playoff game. He also took away one of the Capitals' two nonemergency recalls permitted before the end of the regular season.

"I signed Leinonen according to regulations and to back it up I got a release from the Finnish Ice Hockey Federation," Poile said. "He played in Finland after that date, which the league calls an illegal loan. When they told me the situation, I wanted to use one of my two recalls, but obviously they weren't going to let it go at that.

"I didn't know I was in violation of the rules. My position is that it was a mistake made in this situation by more than one party. I certainly do not agree with the severity of the discipline. The fine far exceeds the crime, if there was one. I can't think of anybody who was ever fined $7,000 for a brawl or anything else."

The NHL recently threatened clubs with $5,000 fines for future altercations at the end of periods. As a result, the Capitals, who had been involved in a free-for-all against Philadelphia, experimented by switching ends, benches and penalty boxes to avoid contact among players leaving the ice. They returned to the old format after one game because of complaints from fans.

Fines levied against individual players for improper conduct are limited to $500 by the agreement between the NHL and the Players Association. Although suspensions would seem to hit the players' pocketbooks more heavily, since they technically are not paid their regular salary, in most cases the club pays them, anyway.

Leinonen is by no means a star. He has not played for the Capitals and might never play for them, but was signed for the rest of this season merely as depth in case of injuries.

Since several other clubs were attempting to sign Leinonen for the same purpose, it would appear that one or more complained to the league and helped to influence yesterday's ruling.

Leinonen, 29, returned to his old Karpat team in Finland this year after spending three seasons with the Rangers. In 159 NHL games, he recorded 31 goals and 77 assists. However, he spent more than half of last season with Tulsa in the Central League.

The Hartford Whalers, who visit Capital Centre tonight at 7:30, have won five straight games . . . The Capitals will put about 2,500 tickets for each playoff game on sale during tonight's contest. If any remain, they will be available at regular ticket outlets Thursday morning . . . Al Jensen is scheduled to play his third straight game in the Capitals' nets tonight, with Pat Riggin listed for Thursday at New Jersey . . . Defenseman Mike McEwen is a doubtful starter because of a sore back incurred when he was tripped Sunday by Pittsburgh's Greg Fox.