VIENNA, Austria (AP) _ Communist authorities in Czechoslovakia have released six human rights activists arrested 10 days ago at a peaceful rally in central Prague, an emigre source reported today.

But banned playwright Vaclav Havel and two other activists remain in custody and, like the six who were released Wednesday in Prague, face trial on charges of disturbing the peace and hooliganism, said the London-based Palach Press, which monitors events in Czechoslovakia.

Havel and 15 other activists were detained on Jan. 16 after eight of them tried to lay flowers in central Wenceslas Square in memory of Jan Palach, a student who burned himself to death there 20 years ago. Palach was protesting the August 1968 Soviet-led invastion that crushed ''Prague Spring'' reforms.

According to the emigre source, the nine accused of disturbing the peace and hooliganism face a maximum of two years in prison if convicted.

The six released were identified as Dana Nemcova and Sasha Vondra, spokesmen for the Charter 77 human rights group, Ms. Nemcova's son David Nemec and Petr Placak, both of the Czech Children group, Stanislav Penc of the John Lennon Peace Club and Jana Sternova, also a senior Charter 77 member.

Besides Havel, those in detention are Jana Petrova of the Independent Peace Association and Otakar Veverka of the John Lennon Peace Club. Havel, 52, has spent a total of four years in prison for his human rights activities.