Around 200 Parisians were arrested after they began throwing things at officers, including candles from one of the floral tributes for those killed in the recent Paris attacks.
In the lead-up to the World Climate Change Conference, protests have been staged in around 2,000 cities across the globe.
But in Paris itself demonstrations have been banned since terrorist attacks by IS militants that killed 130 people.
That didn't stop a small group of anti-capitalism protesters from gathering in the Place de la Republique, chanting slogans against the police emergency powers.
As objects were thrown, riot police formed lines and fired tear gas.
Around 200 people were arrested.
French President Francois Hollande has called their actions "scandalous" after some activists reportedly pelted police officers with candles left at floral tributes for those killed in this month's terrorist attacks.
"This is why these protests are not authorised. We knew there would be troublemakers who have nothing to do with climate activists, or those who want the conference to succeed. They're only there to create trouble. That's why we put several under house arrest. And it's doubly unfortunate, I'd even say scandalous, that it happened in the Place de la Republique, which is filled with flowers and candles placed in memory of those who were killed by terrorists."
Hours earlier, protesters had taken part in a more restrained display, placing over 20,000 pairs of shoes in the Place de la Republique to symbolise their stand against climate change.
Among them was a pair of plain black shoes sent by Pope Francis.
Brazilian Cardinal Claudio Hummes says the Pontiff remains adamant that climate change is a pressing moral issue that must be addressed.
"It's important for all of us because our future depends on it. The way we are now, there is no chance for the future. It's an ethical question we need to ask ourselves: what world will we leave for our children, and for younger generations? That's what the Pope says. What are we going to give to those who want to have a reliable future?"
The conference is hosting 147 heads of state and government and aims to secure binding commitments to reduce global emissions and keep temperature rises to below two degrees Celsius.
Ahead of the conference's formal opening, French foreign minister Laurent Fabius urged all nations to break a 20 year cycle of rivalry that has hampered previous efforts to forge a climate rescue pact.
"Personally, I'm confident you will be able to achieve a good result. However the management of time will be a crucial point. Every day we have to make progress. No subject must be left aside. Therefore, I count on you to negotiate and build compromises as soon as negotiations are taken up again. Your energy, competence and experience should be fully focused on finding solutions."
United Nations Secretary General Ban Ki Moon is also buoyant.
"At this time I'm optimistic that we will be able to have an ambitious and robust universal climate change agreement. I think the stars are aligning in one direction."
But Martin Kaiser, the head of International Climate Politics at Greenpeace, isn't so sure.
He puts the summit's chances of reaching a good outcome at 50-50.
"Here in Paris, they need to have a clear decision about a long-term goal to phase out coal, oil and gas and to enter into 100 per cent renewable energy generation by 2050. With this clear signal and a renewed commitment from all countries every five years we still have a chance to limit global warming far below two degrees."
Oxfam Australia Chief Executive Dr Helen Szoke will be attending the second week of the conference.
She says Australia should keep developing nations in mind when discussing the worst impacts of climate change.
"We're surrounded by developing countries and so many of them are really going to be at the forefront of the impacts of climate change. Australia has a particular responsibility to protect and to help them adapt."
Low-lying island nations in the Caribbean and the Pacific have been at the forefront of calls for tough emissions standards amid rising sea levels.
At the weekend's Commonweatlh Heads of Government meeting in Malta, many issued warnings of disaster if a deal isn't reached.
Among them was the Prime Minister of Barbados, Freundel Stuart.
"When the planet speaks we have no choice but to listen, and the planet has been speaking to us with a daunting eloquence over the last few years, and therefore we go to Paris on the clear understanding that there must be change. If we don't reach a sensible agreement in Paris we can all prepare for a disaster."
SBS reporter Sarah Abo is in Paris, sponsored by the UN's weather agency, the World Meteorological Organisation.
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