Police have banned a rally and march planned for Saturday by the group behind Hong Kong's biggest demonstrations, in an unprecedented move slammed by the organisers who accused the government of "declaring war on all peaceful protesters".

And just hours after the Civil Human Rights Front was informed of the decision, its convenor Jimmy Sham Tsz-kit and his assistant were attacked by two masked men with baseball bats.

The ban, which 

confirmed a Post report on Wednesday

, covered a march and rally scheduled to mark the fifth anniversary of 

Beijing announcing a restrictive electoral reform package

 that was eventually rejected by Hong Kong.

Citing safety concerns, the force officially rejected the front's application to hold a rally at Chater Garden in Central at 3pm and an associated march to Beijing's liaison office in Western district, in a five-page letter.