Anti-war, environmental and pro-jobs groups, linked by their opposition to the policies of the G-20 countries, marched today from Oakland to Downtown to the North Side in a demonstration that featured loud chanting and occasional taunting but, amid heavy security, no violent clashes.

President Barack Obama, joined by heads of state from allies Great Britain and France, issued a strong challenge to Iran this morning to abandon a nuclear program that he said is in violation of international law.

Pageantry, policy and protest jostled for position yesterday as leaders of the world's key economic powers joined President Barack Obama for the G-20 kickoff dinner and discussions while demonstrators skirmished with police across the city.

Police arrested 42 people, and protesters broke windows at 14 businesses in Oakland after authorities dispersed a crowd of anarchists and students who had gathered last night outside a G-20 Summit dinner at Phipps Conservatory.

During a day of protests in Pittsburgh's East End neighborhoods, 24 people were arrested in other actions and five other businesses were damaged. In all the incidents six people, including three officers, had to be treated at hospitals, city police announced today.