"Security forces have freed activist Hella Mewis," Iraq's military spokesman Yahya Rasool said in a statement.

There were no details on the timing of the operation, the force that carried it out or who had kidnapped Mewis.

A spokesman for Iraq's Supreme Judicial Council, Abdelsattar Bayraqdar, said the operation had been backed by a Baghdad investigative court.

"We are still investigating this crime," he said.

Mewis, who ran arts programmes at Iraqi collective Tarkib, was kidnapped late on Monday as she was leaving her office.

"She was riding her bicycle when two cars, one of them a white pickup truck (of the type) used by some security forces, were seen kidnapping her," a security source told AFP.

Police officers at the local station witnessed the abduction but did not intervene, the source added.

Mewis's phone was still unreachable on Friday and her friends had not heard from her.

The German embassy in Baghdad had no immediate comment.

A friend of Mewis told AFP she had been worried following the killing of Hisham al-Hashemi, an Iraqi scholar who had been supportive of anti-government protests last year.

"I spoke to her (Mewis) last week and she was really involved in the protests too, so she was nervous after the assassination," said the friend, Dhikra Sarsam.

Large demonstrations erupted in Baghdad and Iraq's Shiite-majority south last year, railing against a government seen as corrupt, inept and beholden to Iran.

Around 550 people died in protest-related violence, including two dozen activists who were shot dead by unidentified men, usually on motorcycles.

Dozens more were kidnapped, some of whom were later released near their homes. The whereabouts of others remain unknown.

Amnesty International has slammed the incidents as "a growing lethal campaign of harassment, intimidation, abductions and deliberate killings of activists and protesters".

This year has seen a worrying spike in abductions of foreigners, who had not been targeted in several years.

On New Year's Eve, two French freelance journalists were taken hostage for 36 hours and three French NGO workers were held for two months.

In both cases, neither the kidnappers nor the conditions of their releases were revealed.