Austrian authorities have freed one of three people arrested on suspicion of posting a video message on the Internet threatening attacks on Austria and Germany, a judiciary spokesman said.
A fourth person is in custody in Canada in connection with the same case of links to al-Qaeda.
In Austria, a Vienna judge released a 26-year-old man for lack of sufficient evidence that he committed a crime, a judiciary spokesman said.
The judge ruled that the other two suspects, a 22-year-old man and his 20-year-old wife, would remain in investigative custody as a criminal inquiry proceeded, he said.
The man was suspected of trying to coerce Austrian government officials into withdrawing military personnel from Afghanistan by threatening attacks in the video. The man and his wife were suspected of being members of a terrorist organisation as well, he said.
All three people were second-generation immigrants from Arab countries and held Austrian passports.
In Canada, a 35-year-old man was arrested in the French-speaking province of Quebec and charged with plotting to cause explosions in a foreign country.
Austrian officials said earlier the man held in Canada, who they said was of African descent, had been in contact by email and online forums with those arrested in Vienna.
The video message posted in March demanded German and Austrian soldiers leave Afghanistan, but in electronic surveillance over several months police found no concrete indications that attacks were in the offing.
The arrests came a week after Germany said it foiled an Islamist militant plan to carry out "massive bomb attacks" on US installations in the country. Germany arrested three men.
The Austrian Interior Ministry said it knew of no links between the German and the Austrian suspects.
Austrian authorities said they decided to close in on the suspects after learning that the man and wife were about to leave the country to go to Egypt for their honeymoon