Danish Justice Minister Brian Mikkelsen presented a series of measures Monday aimed at cracking down on any violent protesters at the UN climate conference in Copenhagen in December.

Demonstrators who disrupt the peace will be fined up to five times the usual amount and in some cases be sentenced to jail time, Mikkelsen told reporters.

The government will not allow a conference of that scale to be "drowned in troubles and destruction," the minister said in a statement.

"These strict measures apply only to protesters who aim to create problems, who commit acts of vandalism and prevent the police from doing their work," he added, emphasising that Denmark was "the best example of freedom of expression."

The special measures will allow police to detain potential troublemakers for 12 hours, double the current time. Protesters who prevent the police from doing their work could face up to 40 days in jail, the minister said.

His proposals still need to be approved by the Danish parliament, but will certainly go through as they are backed by the far-right Danish People's Party, which provides crucial support in parliament to the minority centre-right government.

The December 7-18 talks in Copenhagen, under the 192-nation UN Framework Convention on Climate Change (UNFCCC), aim to craft a post-2012 pact for curbing the heat-trapping gases that drive perilous global warming.