Eva Maria Michelmann initially went missing in January during an offensive by Syrian government fighters in the northeast of the country, which had previously been controlled by Kurdish forces.

Reports at the time said she had been taken in a vehicle belonging to government troops in the city of Raqqa, along with Turkish-Kurdish journalist Ahmed Polad.

According to the Committee to Protect Journalists (CPJ), they both worked for the Istanbul-based socialist Etkin News Agency (ETHA) and the Ozgur TV channel.

On Friday a German foreign ministry spokeswoman said that Berlin was making "intensive representations" in the case at a "high level".

"Employees of the German embassy in Damascus have recently been able to make visits (to Michelmann) in detention," after an initial visit in April, the spokeswoman said.

However she was not able to say why Michelmann was being detained and whether Syrian authorities had charged her with any crime.

Last week Michelmann's German lawyer said she was in a "bad condition" in detention.

Roland Meister told AFP that he had received reports of Michelmann being "tortured and subjected to constant interrogation, including at night" and that she had "lost a lot of weight".

The CPJ has condemned "the Syrian government's lack of transparency regarding the detention and whereabouts" of the two journalists as "unacceptable".

It says the case "raises serious concerns about press freedom in Syria".

The group in late April also decried Polad's "continued enforced disappearance", adding that some sources had suggested that he may be held in a prison in Aleppo.