Breyten Breytenbach, the most prominent poet and author in the Afrikaans language of South Africa's ruling white group, has been released from prison after serving seven years of a nine-year sentence for subversion.

He flew last night with his Vietnamese wife to Paris, where he had spent 13 years in self-imposed exile before being arrested in 1975 on a clandestine visit to South Africa where he was recruiting for the African National Congress. The congress, which is seeking to overthrow South Africa's white rule, was banned here in 1960.

Breytenbach, 44, is the first political prisoner to be granted early release. Time off for good behavior is normally granted to ordinary criminal offenders, but until recently it was government policy that anyone jailed under the country's wide-ranging security laws had to serve his full sentence. For many, this means imprisonment for life.

Earlier this year Minister of Justice Jacobus Coetsee announced the introduction of a new review system that made it possible for political prisoners also to get time off, but it has not been used until now.

Less than a month ago a young white journalist, Anthony Holiday, was released after serving the whole of a seven-year sentence for distributing pamphlets for the congress.

Breytenbach's early release is all the more surprising because the Afrikaner government tends to be particularly unrelenting toward dissenters of its own language group, whom it considers ethnic traitors.

This attitude was reaffirmed in October when a five-year banning order was renewed for another three years on a prominent former minister of the Dutch Reformed Church, C. F. Beyers Naude, despite widespread appeals that he be freed.

There also were appeals for Breytenbach's release, mostly from other Afrikaner literary figures who regard him as an important cultural leader.

There is no explanation why Breytenbach was shown clemency and not Naude. However, in both cases the ministers concerned would have acted on the advice of the security police.

In Paris, the French Foreign Ministry said that it had exerted vigorous efforts for the poet's release, Reuter reported.

A statement on Breytenbach issued by the Justice Department last night said: "Decisions of this nature are the result of the total profile that is formed of a person's background, behavior, adjustment, attitude, possible future behavior and the expected risk or threat that such a person may pose to the community after release."

The department also made clear that "no hope for remission of sentence or conditional release whatsoever can be cherished for other persons who persist in their original criminal objectives."

Breytenbach was freed Thursday, but his release was kept secret until last night when he left the country after spending two days visiting his parents in eastern Cape Province.

That is when the department issued its statement, which also indicated that Breytenbach would have been allowed to live unrestricted in South Africa had he not gone to Paris and that he could return.

Breytenbach, a romantic who writes sensitive and sometimes sensuous poetry that has broken new literary ground for the Afrikaans language, became involved with a branch of the African National Congress while living in exile.

In 1975 Breytenbach flew to South Africa in disguise on a mission for the group to recruit young Afrikaner dissidents. He was arrested within days.