Aboriginal tent embassy protesters have burnt the Australian flag at the front steps of Parliament House as tensions surrounding the controversial protest site erupted in Canberra today.

The escalation came as Prime Minister Julia Gillard said she was unaware of claims one of her staffers may have triggered yesterday's ugly Aboriginal protest, which culminated in her being dragged from a Canberra restaurant by her security team.

Protesters burn the Australian flag outside Parliament today. Credit:Andrew Meares

A crowd of at least 400 protesters this afternoon marched from Old Parliament House up Commonwealth Avenue and stormed the front verandah of Parliament House about 2.30pm, despite a large police presence.

The crowd was blocked from entering Parliament House by a 60-strong human wall of special response and armed police, which have locked down the building to all visitors.