CHUR, Switzerland (AP) _ The grandson of West German publisher Axel Springer disappeared from a Swiss boarding school and police assumed he had been kidnapped, but the publishing company announced Wednesday night that he was free.

It said Sven-Axel Springer, 19, was met at Zurich airport at 9:40 p.m. The announcement from Springer's office gave no further details were given.

Swiss police had announced earlier in the day that Springer had vanished last weekend from the boarding school he was attending in an alpine resort and that it was assumed he had been kidnapped.

A Swiss police communique said the family of the youth was informed by a tape-recorded message in his voice that a ''high ransom'' had been demanded for his release. Police sources in Munich, West Germany, who insisted on anonymity said the demand was for 15 million marks, roughly equivalent to $5 million.

The police communique said Springer was last seen Sunday and that it was assumed that he was kidnapped during the night.

It quoted the tape as saying, ''I have been abducted Sunday night. Press and police must not be informed, otherwise I will be killed.''

The news media were informed of the reported kidnapping early Wednesday but heeded a request by the victim's family and the police not to publish information on the case. But the Swiss news agency SDA published the report during the day and the Swiss police issued a statement.

The youth is a student at a boarding school in the fashionable resort at Zuoz.

Axel Springer is publisher of the conservative West German newpapers Bild and Die Welt and a frequent target of left-wing criticism.

Springer publishing houses in both West Berlin and Hamburg were damaged by demonstrators in the early 1970s. In 1975, a luxurious chalet he owned near the Swiss resort of Gstaad was destroyed by fire and police then said they assumed it was arson. The case remained unresolved.

Sven-Axel is the son of Sven Springer, an internationally known photographer and photo agency director who committed suicide several years ago.