(CNN) -- Danish police made around 250 arrests in Copenhagen Wednesday morning as an organized demonstration against the U.N. climate talks converged on the Bella Center ahead of crucial negotiations at the COP15 summit.
Kristina Larsen, a spokeswoman for Climate Justice Action (CJA) -- the group organizing the protest -- told CNN that police have used pepper spray and dogs to contain the protests.
Around 3,000 activists convened at two railway stations in the Danish capital early on Wednesday and began their march towards the Bella Center -- the scene of the climate talks.
CJA is calling for activists to "take over the conference for one day and transform it into a 'People's Assembly'."
At the same time protesters were marching towards the U.N. summit, a number of delegates were planning to walk out of the Bella Center.
Larsen told CNN: "Around 300 people have marched out of the Bella Center shouting 'reclaim power'."
But the planned "People's Assembly" which was due to take place outside the building has, so far, been disrupted by the police.
Reporting from inside the Bella Center CNN's Phil Black said that several hundred activists were near the perimeter of the conference center.
"There have been some clashes and scuffles, and the police have fired some tear gas, but the protests have been reasonably low-level." Black said.
CJA say they are holding a "People's Assembly" to counter the "false solutions and elitism of the U.N. climate talks."
A spokesman for the Copenhagen police told CNN that the majority of arrests have taken place outside the Bella Center but there have been no serious injuries.
"The protesters detained have been taken to a temporary holding facility and most are expected to be released in the next two hours," the Police spokesman said.
On Sunday, police said they had detained 968 people, accusing protesters of donning facemasks, throwing fireworks and stones, breaking windows and setting vehicles alight. A further 212 people were arrested overnight on Monday.
CJA says that protesters are engaged in "peaceful, nonviolent protest" and accused the police of being "out of control."
"We've had a lot of police repression in the last couple of days," Larsen told CNN. She also claimed that the environmental group Friends of the Earth had been denied access to the Bella Center on Wednesday morning.
While the protests were going on outside, inside it was being announced that Danish minister Connie Hedegaard had resigned as president of the U.N. climate change summit.
"The resignation is essentially procedural," CNN's Phil Black said, "and she'll be replaced by the Danish prime minister. It's a reflection of the fact that the talks are now at the high-level phase, and it was deemed appropriate that the PM should now take over."
World leaders have started arriving in Copenhagen for the final days of "high-level" negotiations. British Prime Minister Gordon Brown was among the first to arrive, holding talks Tuesday with Australian and Bangladeshi counterparts Kevin Rudd and Sheikh Hasina. U.S. President Barack Obama is expected to arrive Friday.
U.N. Secretary-General Ban Ki-moon told nations Tuesday that they had the chance to "change the course of our history" if they worked together to limit carbon emissions that are blamed for increasing global temperatures.
"We have a chance -- a real chance, here and now -- to change the course of our history," he said, noting that countries had to work quickly, because nature doesn't negotiate.
He urged both industrialized and developing countries to do more during this week's Copenhagen summit toward reaching an agreement on limiting the emissions, saying they "can and they must do more."
"This is a time to stop pointing fingers," Ban added. "This is a time to start looking in the mirror and offering what they can do more of."
U.S. Secretary of State Hillary Clinton wrote Tuesday that the United States is ready to do their part to reduce greenhouse-gas emissions but that other countries, especially poorer ones, must play their parts as well.
Clinton's assertion came as a major international summit headed into the home stretch. "Nearly all of the growth in emissions in the next 20 years will come from the developing world," Clinton wrote in an opinion piece for the International Herald Tribune. "Without their participation and commitment, a solution is impossible."
The divide between rich and poor countries is one of the key fissures at the conference.
Developing countries object to restrictions that they fear would keep them from following the same path to prosperity taken by the United States and other industrialized nations.
The man running the conference warned Tuesday that "nowhere near enough progress" had been made toward an agreement.
"There is still an enormous amount of work and ground to be covered if this conference is to deliver what people around the world expect it to deliver," Yvo de Boer, executive secretary of the U.N. Framework Convention on Climate Change, said at a news conference.