At least 36 people have been arrested after protesters and police clashed in Rome a day ahead of the Group of Eight (G8) summit.
Demonstrators hurled bottles at riot police and set fire to tyres on the streets of the Italian capital on Tuesday, news agencies reported.
The clashes came as leaders from some of the world's richest nations gathered in the city ahead of the summit, which begins on Wednesday, aimed at tackling the global economic crisis, climate change and events in Iran.
Italian police were on high alert on the eve of the summit, with 15,000 officers deployed in an effort to prevent a recurrence of the violence seen during the country's last G8 meeting in 2001.
Police and soldiers are guarding a converted police barracks where the leaders will meet in L'Aquila, where more than 150 people died when an earthquake struck the town in April.
Silvio Berlusconi, the Italian prime minister, announced in April that the meeting would be moved from Sardinia in an effort to save funds that could be used to help reconstruct the devastated area.
Officials have drawn up plans to evacuate the leaders and cancel the summit if any tremour measuring more than four points on the Richter scale strikes the region.
The bulk of the summit is likely to focus on efforts to shore-up the global economy since leaders committed $1trn at the G20 summit in London to help struggling economies and revive global trade.
The talks will also focus on emerging political crises in China's Xinjiang region, Iran and Honduras.
Angela Merkel, the German Chancellor, said she would speak to Hu Jintao, China's president, about the worsening ethnic violence in his country, in which at least 156 people have been killed.
"We will have the opportunity to address these questions with the Chinese president in L'Aquila," she said on Tuesday. "I will use this opportunity".