Seven men accused of posing as a self-styled "Sharia police" in Germany have gone on trial for the second time, on charges they violated rules on wearing uniforms.

News agency dpa reported that none of the defendants, aged between 27 and 37, addressed the charges against them as their retrial in Wuppertal opened Monday.

The group took to the streets of Wuppertal in 2014, dressed in orange vests bearing the words "Sharia police" and handing out leaflets declaring the area a "Sharia-controlled zone" where alcohol, music and pornography were banned.

Five were allegedly part of the self-styled patrol and the other two accessories.

They were acquitted in 2016 when judges found that the vests couldn't be classified as a uniform and weren't intimidating. A federal court ordered a retrial.