U2 [ tickets ] frontman Bono [ tickets ] made a surprise appearance with Pearl Jam [ tickets ] Friday (11/17) during an outdoor concert in Melbourne on the eve of the G-20 economic meetings set to take place in that city.

The outspoken Irish singer/activist used the occasion to protest the meetings and call for an end to world poverty.

"Politicians have to do what you tell them to do. We are gonna make poverty history," Bono said, according to Australian news reports, before launching into a cover of Neil Young's "Rockin' in the Free World" with the Seattle grunge-rock veterans.

Three days of potentially violent protests are expected during the meetings, which continue Saturday and Sunday. Police have locked down parts of Melbourne, Australia's second-largest city, in hopes of containing possible flare-ups.

Bono and Pearl Jam were performing as part of a benefit for Make Poverty History, an organization--very vocally supported by the singer in the past--that campaigns for countries to forgive debts of poor and developing nations, among other concerns. Thousands of people were in attendance at the concert, which was beamed live via satellite to locations around the world, according to news reports.

The G-20 is a group consisting of economic leaders and finance ministers from the 20 largest global economies. The group meets once every year in a different member city to discuss international cooperation regarding economic issues.

The group has been a lightning rod of criticism for anti-globalization foes, who view the organization as having too much influence over the world's economy, and worry that its existence promotes the enrichment of member states at the expense of developing nations around the globe.

Authorities were expecting up to 20,000 people to attend a protest march on Saturday in the city's downtown business district. A group calling themselves "The G20 Christian Collective" set up a "pray embassy" behind police barricades, according to Australian media reports.

"We think it's obscene that the world's finance ministers are the ones who are making the decisions about what happens in our world, and we think the voices of the poor need to be heard and certainly the voices of those who know about the environment," an anonymous member of the group was quoted as saying.

U2 was set to play back-to-back concerts in Melbourne over the weekend. Pearl Jam, not currently touring, is scheduled to open for the Irish band at its Dec. 9 show in Honolulu.