One Nation leader Pauline Hanson has declared she is not a racist during a rally against Islam in Brisbane.

Ms Hanson, who narrowly lost her fight for a seat in the 2015 Queensland election, joined hundreds of protesters in King George Square.

Many were draped in the Australian flag and carried signs denouncing sharia law and halal certification for Australian products.

The group Reclaim Australia is holding nationwide rallies against "sharia law, halal tax and Islamisation".