A teenager whose family home burned down in the New South Wales bushfires has delivered a message to Scott Morrison at a climate emergency protest outside the Liberal party headquarters, saying: “your thoughts and prayers are not enough”.

Shiann Broderick, from Nymboida, said government inaction on the climate crisis had “supercharged bushfires”.

“People are hurting,” she said in a statement before the protest on Friday at the party’s Sydney headquarters on Friday. “Communities like ours are being devastated. Summer hasn’t even begun.”

The protests were part of an international day of climate strikes, the movement founded by Swedish teenager Greta Thunberg.

Later, protesters chanting “fuck BHP” gathered around the mining company’s Australian headquarters in Melbourne.

The protest was organised by University Students for Climate Justice, one of the groups involved in a two-day protest of an international mining conference in Melbourne, which saw one protester trampled by a police horse, several hit with capsicum spray, a dozen people arrested, and provoked public criticism about the severity of the police response.

Police stood by their actions, supported by the Victorian premier Daniel Andrews, but later said they were “disappointed” in the actions of two of the officers, including one who put a sticker on his body camera saying “EAD hippies]”.

Students in Adelaide gathered outside the South Australian Exploration and Mining Conference.

In Darwin protesters gathered outside the office of chief minister Michael Gunner and in Hobart a crowd rallied on the lawns outside state parliament.

The protests on Friday followed massive protests in September, when hundreds and thousands of people across Australia joined the school strike movement.

This time, the strikes were focused on the impact of devastating bushfires in New South Wales, Queensland, and Victoria in which six people have died and more than 600 homes have been destroyed.

They are calling for no new coal, oil or gas projects to be built in Australia, a transition to 100% renewable energy by 2030, and funding for a just transition for fossil fuel workers and communities.