A 16-year-old Danish girl who recently converted to Islam, was charged for planning a terror attack against a Jewish school in Copenhagen and another school in Denmark.

A police press release said the girl's 24-year-old friend, who local media have said was a former fighter in Syria, had also been charged with complicity in preparing the bombs.

A Danish prosecutor said that the suspects, who have not been identified, obtained chemicals and tried to produce explosives with the intent to commit terror attacks against the two schools.

He said police thwarted their plans by arresting them. He declined to give other details.

The Danish intelligence service said the arrests had not changed their assessment of the security threat, classified as "serious" since February 2015 when a gunman killed two people in shooting attacks on a debating event and a Copenhagen synagogue before being shot dead himself by police.