Climate change demonstrators took to the streets of Warsaw during the weekend as host Poland comes under fire from critics at the U.N. COP19 climate summit.

Chanting "Change the system, not the climate," and "Justice and positive energy for all," nearly 1,000 people marched through Warsaw Saturday as part of the international "March for Climate and Social Justice," the Polish broadcaster TVN 24 reported.

The event caused traffic congestion in the heart of the city as it wound its way from the Palace of Culture and Science, passed over the Poniatowski Bridge along Jerusalem Avenue and past the National Stadium, where the UN climate summit is being held.

The march ended at Skaryszewski Park near the National Stadium, where demonstrators set up an "eco-park."

At the head of the procession was a large inflatable globe, emphasizing the demonstrators' point decisions made to reduce greenhouse gases at the summit this week will affect the lives of many generations to come.

Calling for significant but "fair" emissions reductions spread among all countries, the marchers blamed global warming for severe weather events and urged the world's nations to quickly institute renewable energy, energy efficiency and reductions in consumption.

At the same time, they declared, societies adapting to climate change must also take into account the fate of workers in economic sectors doomed to disappearance because of the switch-over.

The Polish news agency PAP reported the demonstration was attended by representatives of Polish environmental organizations working for climate protection, as well as by opponents of open pit mines, shale oil and gas and nuclear power.

Farmers, social activists and trade unionists also attended, as did leaders of the Greens in the European Parliament as well as leaders of social movements from around the world, including from the Philippines.

The march came as Poland was taking criticism from environmentalists and world leaders at the Warsaw Climate Change Summit, which runs through this week.

Samantha Smith, leader of the WWF's Warsaw delegation, told The Financial Times its lack of enthusiasm for big emissions cuts due to its continued reliance on coal -- along with the backtracking of several other nations on targets -- were making for an downbeat summit.

She made the comments Friday after Japan announced its ambitious reduction goals had become untenable due to the Fukushima nuclear disaster of 2011, asserting it would have "a negative impact on the conference"

A Polish presidency official, however, told the newspaper Smith's reaction was "hysterical," adding, "most delegations have taken this pretty calmly."

Poland also came under attack last week for arranging a coal industry summit to be held concurrently in the city, inviting polluting industries to sponsor it.

Polish Environment Minister Marcin Korolec, who is also serving as the COP19 chairman, defended the move, claiming that inviting businesses to the conference made it "broad and inclusive," the Chinese news agency Xinhua reported.

He asserted the sponsorship deals for the coal summit were "transparent."

But Julia Michalak, a policy officer at Climate Action Network, told Britain's Responding to Climate Change blog Poland was guilty of "grossly misusing its position as COP president."

"By endorsing and co-hosting a coal summit in the shadows of the UN's climate change negotiations Poland has proven it prefers to push its own selfish interests, and those of the coal industry, rather than working collectively to achieve a global climate deal by 2015," she said.