Police have arrested dozens of protesters during climate change demonstrations across the nation on Monday, including elderly activists who were dragged away by force.

Key points: Extinction Rebellion protests are planned for Sydney, Brisbane and Melbourne

Extinction Rebellion protests are planned for Sydney, Brisbane and Melbourne They're calling for the Government to do more to tackle climate change

They're calling for the Government to do more to tackle climate change NSW Police said the group was known for "causing significant disruption to the community"

There were 38 arrests in Sydney, with charges including failing to comply with direction, while in Melbourne 10 people were arrested for failing to obey move on orders and seven protesters were arrested in Brisbane.

The rallies, organised by the Extinction Rebellion movement, are calling for more government action on climate change.

Hundreds took part in the Sydney demonstration which began at Belmore Park near Central on Monday afternoon.

Several elderly protesters were led away, including a man in a suit, whose removal prompted two men to lie down on Broadway in protest against the police intervention, before they too were removed.

One woman was placed in handcuffs and had her arms pulled over her head by officers as she was led away.

Police arrest a man during the protest in Sydney. ( ABC News: Selby Stewart )

An elderly woman screamed, "You're hurting me, please stop this," as police dragged her away, after she refused to leave the road.

Protesters chanted, "This is what democracy looks like" and called those being led away "heroes".

Police on horseback watched on as officers removed five teenage girls from the road, ending the sit-in protest.

Protesters lay on the road during the rally in Sydney. ( ABC News: Selby Stewart )

The rally then moved to Central Park where protesters held hands, chanted and sang songs.

Four protesters chained themselves inside a makeshift water tank before police and a tow truck removed the tank and cut the protesters free.

New South Wales Police said 30 people were arrested following the rally, for offences ranging from obstructing traffic to disobeying reasonable direction.

Police kept a close watch as protesters prepared to set off from Carlton Gardens in Melbourne. ( ABC News: James Hancock )

Assistant Commissioner Mick Willing said officers' priority was to ensure public safety.

"While police respect the right of individuals and groups to protest, we have a responsibility to the community and local businesses to ensure they can go about their normal activities without being impacted on or put at risk," he said.

"We are aware that this particular group of protesters intend to cause significant disruption to the community, and any future activity of this nature will not be tolerated by NSW Police."

Extinction Rebellion activists march in Brisbane. ( AAP: Regi Varghese )

Several hundred protesters marched through central Brisbane amid heavy police presence.

Some activists blocked Victoria Bridge by locking on to a timber structure in the centre of the road.

A Queensland Police spokesman said seven people were charged, including for allegedly contravening police directions, walking onto a roadway when not authorised, obstructing police and public nuisance.

In Melbourne, protesters blocked the entire intersection at Flinders Street causing peak hour traffic disruptions.

Activists also gathered at the Carlton Gardens, in the city's north and marched into the CBD where hundreds staged a sit-in in the busy intersection of Russell and Bourke streets.

A woman is dragged away by police. ( ABC News: Selby Stewart )

Some carried a glass coffin, like a fish tank, filled with aquatic plants and rocks to illustrate their concern about the impact of climate change on oceans.

Protesters were briefed before setting off and were given a legal support number in case they were arrested during the protests.

Earlier, at the Victorian Parliament a handful of people sat on the steps a meditated for climate change.

Victoria Police said 10 protesters were arrested. Eight were issued with a penalty notice for obstructing a highway and two were charged with intentionally obstructing an emergency worker.

More protests planned

Extinction Rebellion Southeast Queensland spokeswoman Emma Dorge said the group expected thousands of people to join in civil disobedience during the week.

The Flinders Street intersection comes to a standstill. ( ABC News: James Hancock )

She said this would include protesters pitching tents and camping throughout Brisbane's CBD.

"We are sorry for individual inconveniences to people [but] our goal is the economic disruption of big business and government who are exploiting all of us and sacrificing our futures for short-term profit," she said.

Ms Dorge said protesters were not deterred by Queensland Government moves to toughen penalties, and suggestions by federal minister Peter Dutton to mandate jail and cut welfare for people who disrupt traffic.

"Our numbers have only been growing despite the backlash that we've received because people are terrified about the climate crisis, they know what's going on, and they're looking for a viable avenue to create change," she said.

Police said 30 people were arrested at the Sydney protest. ( ABC News: Selby Stewart )

Dr Christine Canty, co-ordinator of Extinction Rebellion Families told ABC Radio Melbourne the city's Carlton Gardens would have a "festival atmosphere" this week where the public could "come and find out what Extinction Rebellion is all about".

"We're sorry that the disruption is the only way to be going about this but activists, over 30 years, have tried everything else and this is a last resort," she said.

"Scientists are telling us now unequivocally that change is exactly what we need. Assertive change now to prevent complete ecological and climate breakdown.

"We really just have no other choice at this point."

She denied suggestions published in The Age newspaper that Extinction Rebellion had been infiltrated by "fringe groups".

"I'm not aware of any infiltration from other groups," she said.

"We know that violence is not the way to get our message out and anyone acting in the name of Extinction Rebellion is certainly well aware of that and embodying that with everything we do."

Climate activists "meditate for climate" protested outside the Victorian Parliament. ( ABC News: James Hancock )

ED NOTE: A photo caption has been amended as the image did not depict a woman being dragged across the road on her knees, as initially stated.