Paris -- Kicking off with thousands gathering on the steps of Sydney's iconic Opera House, global warming protests took place around the world Saturday to mark 50 days before the UN climate summit.

From Asia to Europe via the Middle East, activists staged lively events addressing world leaders and to mobilise public opinion around climate issues.

Many waved placards bearing the logo 350, referring to 350 parts per million (ppm) of CO2 in the atmosphere which scientists say must not be exceeded to avoid runaway global warming.

France's politicians received a "wake up" call from several hundred Parisians who chose clocks as their symbol.

Protesters who met in a central square had set their alarm clocks and mobile phones to ring at 12:18 pm local time in reference to the closing date of the summit, which lasts from December 7-18.

The summit is considered crucial as world leaders will try to thrash out a new treaty to curb greenhouse gas emissions in place of the Kyoto Protocol which will expire in 2012.

However, Danish Prime Minister Lars Loekke Rasmussen said Saturday that preliminary discussions are not moving fast enough for an international decision to be concluded in Copenhagen.

"It is time to give full speed to the negotiations," Rasmussen said, adding that he wanted a legally binding international agreement to be in place by January.

There is growing concern that a treaty deal in Copenhagen could be hampered by issues including US domestic politics and the problems of securing agreement between developed and developing countries.

Rasmussen underlined that progress had been made on climate issues but that these "key political questions" still had to be resolved ahead of the December meeting.

In Berlin, some 350 protesters wearing masks with the face of German Chancellor Angela Merkel came together in front of the Brandenburg Gate in the city centre.

In the Lebanese capital Beirut hundreds of activists, many wearing snorkels, held demonstrations in key archaeological sites.

They gathered around the Roman ruins in central Beirut, in the ancient eastern city of Baalbek and along the coast, carrying placards bearing the logo 350.

"It's not the first time Beirut will have gone under water," Wael Hmaidan of the IndyACT group organising Beirut's protests said to AFP, explaining the goggle-wearing, "but this time it's going down because of climate change, and not earthquakes."

In Jakarta, around 100 students from the London School of Public Relations also gathered to form the symbolic number 350, coordinator Candy Tolosa said on Detik.com news website Saturday.

In central Madrid, the Spanish capital, members of the Platform Against Climate Change, grouping social organisations, ecologists and unions, acted out parodies of the "catastrophic consequences of climate change on the planet," the Platform's press release said.

Environmental activists in the Turkish metropolis of Istanbul staged their protest in a boat, unfurling a banner reading "Sun, wind, right now!" under the main bridge linking Asia and Europe over the Bosphorus Strait, Anatolia news agency reported.

They then sailed to the ancient Maiden's Tower, which sits on a tiny islet in the Bosphorus, and unfurled another banner reading "Jobs, climate, justice," the report said.

AFP/Expatica