The German military on Friday said it had grounded nearly half its fleet of Tornado reconnaissance jets, used in the fight against the Islamic State group, because of a technical defect.

In total, 39 of the country's 85 Tornado aircraft have been affected by the defect involving "loose screws on a monitor in the cockpit", DPA news agency reported, citing a Bundeswehr spokesman.

It is the second major embarrassment involving the aircraft after the army in January said the six Tornado jets used for reconnaissance missions over Syria couldn't fly at night because of a problem with the cockpit lights.

The six Tornados stationed at a NATO airbase in southern Turkey are among those that have been grounded over the latest defect, DPA said.

The army spokesman was quoted as saying that the problem had been discovered on Wednesday and that it was not clear how long it would take to fix it.

The German army, which complains of being overstretched and underfunded, has been dogged by a series of equipments failures.

Its G36 assault rifle -- which is being phased out -- became the butt of jokes last year after reports it had trouble firing straight at high temperatures.

In another high-profile setback, the external fuel tank of one of its Eurofighter combat planes fell off as it was preparing for takeoff.