Protective masks will be required on public transport in most parts of Germany, with capital Berlin joining a wave of federal states in ordering the measure to stem contagion of the novel coronavirus. 

A sign advertising the sale of FFP2 protective face masks is taped to a lamppost in Berlin March 4, 2020. (Photo: AFP)

Berlin mayor Michael Mueller told reporters that "to be able to protect people" in trains, busses and trams, his city government intended to make "protection of the nose and mouth compulsory from April 27".

Unlike in shops, it was "not possible to ensure a distance of several metres between each person" in public transport, he said.

Following similar announcements from states including Bavaria, Baden-Wuerttemberg, Hamburg and Hesse on Monday and Tuesday, ten of Germany's 16 regions have now announced similar rules. 

Mueller and other state premiers were keen to emphasize that improvised masks would also be acceptable. 

"I said protection of the nose and mouth...it can also be a scarf," said the Berlin mayor.

Though the new rule will be limited to public transport in Berlin, other states such as Bavaria, Hesse Baden-Wuerttemberg have also made covering up compulsory in shops.

And while the capital will only introduce the measures from next week, others such as Saxony are already enforcing them. 

The move to make masks compulsory comes after Germany began to cautiously lift coronavirus restrictions from Monday, with shops under 800 square meters allowed to reopen in most states.

Following a meeting with state premiers to agree the new relaxations last week, Chancellor Angela Merkel said she "strongly recommended" wearing a mask on public transport and in shops. 

On Friday, Saxony and Mecklenburg-Western Pomerania became the first states to announce they would make masks compulsory. 

By Tuesday, ten states had followed suit, affecting nearly 49 million Germans, over half the country's population. 

Among those yet to introduce the measures are the city of Bremen and the region of North-Rhine Westphalia, Germany's largest state by population.

Germany last week announced plans to ramp up domestic production of masks to 50 million a week by August, including 10 million of the more protective FFP2 standard and 40 million surgical masks.