G20 leaders begin arriving for summit

U.S. President Barack Obama and British Prime Minister David Cameron arrive in Toronto. (Charles Dharapak/Associated Press)

By CBC News

G8 leaders have begun their trip south from Ontario's Muskoka region to gather with their counterparts in the G20 in a heavily fortified and protest-filled downtown Toronto.

The leaders of the eight top industrialized nations who attended this week's G8 summit in Huntsville will be joined in Toronto by leaders from emerging economies such as China, India and Brazil, as well as United Nations Secretary General Ban Ki-moon.