Four people stood on the roof of the building for about an hour, rolling out several banners, with slogans such as “No peace on stolen land” and “From the river to the sea, Palestine will be free.”
Police said the protesters were arrested and expected to be charged with trespassing.
“This is a serious breach of the Parliament’s security,” shadow Home Affairs spokesperson James Paterson said in a post on X. “The building was modified at great expense to prevent incursions like this. An investigation is required.”
Prime Minister Anthony Albanese condemned the protests, saying, "Those responsible should feel the full force of the law. Peaceful protest has an important place in our society, but this was not a peaceful protest."
Inside the building, Fatima Payman, a senator in the ruling Labor Party, quit the party to sit as an independent after she was suspended for voting for a motion backing Palestinian statehood.
Australia, which has called for a cease-fire in the conflict that began last October, does not recognize Palestinian statehood.
Israel has killed nearly 38,000 Palestinians since an Oct. 7 cross-border attack that claimed 1,200 lives. Israeli actions have triggered a humanitarian disaster and an ongoing trial over alleged genocide at the International Court of Justice.