Thousands of extra police are on duty in Pittsburgh

Trouble has flared as world leaders gather in the US city of Pittsburgh for the G20 summit.

Reports said riot police used pepper gas and fired rubber bullets at protesters on a march near the venue.

Demonstrations were widely expected and thousands of extra police are on duty. The previous G20 meeting, in London in April, was marred by clashes.

Economic stability, financial regulation, climate change and bankers' bonuses are set to top the G20 agenda.

The clashes are thought to have begun after hundreds of protesters tried to march, without permission, towards the convention centre where the summit is being held.

'Party over'

With many major economies beginning to climb out of recession - attention will turn to when and how to withdraw government stimulus packages.

Cracking down on bankers' bonuses has popular appeal with the public, it is expected that an agreement will be reached on how that might be achieved.

US Treasury Secretary Timothy Geithner said G20 countries had reached a consensus on the "basic outline" of a proposal to limit pay and bonuses by the end of 2009.

Each country would set their own standards, he said, but that these would be overseen by the G20's Financial Stability Board - made up of central bankers and regulators.

http://news.bbc.co.uk/2/hi/business/8274046.stm