Leaders from around the world are beginning to arrive in Canada for the G8 and G20 summits amid unprecedented security at the two host sites in Ontario.

Nigerian President Goodluck Jonathan arrives at Toronto's Pearson International Airport on Wednesday for the G8/20 summits. Nigerian President Goodluck Jonathan arrives at Toronto's Pearson International Airport on Wednesday for the G8/20 summits. (Dave Chan/Canadian Press)

Chinese President Hu Jintao met with Prime Minister Stephen Harper in Ottawa on Thursday.

A slew of other leaders and delegates are to arrive throughout the day and on Friday will begin three days of intense meetings at Muskoka's Deerhurst Resort and a convention centre in downtown Toronto.

Motorcades carrying leaders from Toronto's Pearson International Airport brought traffic on roadways to a near-standstill throughout the day.

Meanwhile in the downtown core, residents and workers near the G20 site faced the maze of barricades and police checkpoints with quiet resignation.

The summits will allow world leaders to take stock of the global economy following last year's financial crisis, while Harper is expected to pressure some leaders to reduce their countries' high debt levels.

The prime minister also said his government, as G8 host, will push for a global maternal and child health initiative for developing countries, although it has come under fire for excluding abortion funding from the plan.

G8 falling short on Africa AIDS funds: Lewis

As the world leaders began arriving in Canada on Thursday, a prominent voice in the fight against HIV and AIDS in Africa accused the G8 of a "demented passivity" on the issue.

Stephen Lewis, Canada's former ambassador to the United Nations, said upward of nine million people infected with HIV/AIDS are unable to get treatment in Africa and that the G8 has fallen short on its promises to the continent by at least $10 billion.

"You would think that leaders of Western countries who understand what's happening on a continent like Africa wouldn't need to be pushed or bullied or pummeled," Lewis told CBC News on Thursday,

"If they come out of this G8 without delivering on the promises on Africa, they'll have blood on their hands. I don't know how else to describe it."

On Friday, Harper will officially welcome the leaders of the seven other G8 nations — France, Germany, Italy, Japan, Britain, the U.S. and Russia — before the leaders join G20 delegates in Toronto on Saturday.

Britain's David Cameron and Japan's Naoto Kan will make their debuts as leaders at the summits, while Wayne Swan, Australia's new deputy prime minister, is expected to represent his country's new leader, Julia Gillard, following the ouster of Kevin Rudd as prime minister and leader of the ruling Labor Party.

Demonstrations in Toronto, Ottawa

Critics have also lambasted Harper's government over high security costs for the summits, which are expected to surpass $1 billion.

The government has defended the amount, saying such spending is necessary for protecting leaders, as well as thousands of delegates and reporters.

Dozens of police officers with bicycles kept watch as several hundred First Nations protesters marched peacefully on Toronto's Bay Street on Thursday to draw attention to aboriginal issues ahead of the summits.

The marchers shouted, "No G20 on stolen native land!" while carrying placards, banners and Mohawk Nation flags, as well as the upside-down Maple Leaf.

Meanwhile in Ottawa, rival groups of demonstrators greeted the Chinese president as he arrived at Rideau Hall for a meeting with Gov. Gen. Michaëlle Jean.

Hundreds of Hu supporters, reportedly recruited from around the region by Chinese officials, lined Sussex Drive outside Jean's residence, waving flags and banging drums and cymbals.

Directly across the road, protesters connected to the Falun Gong spiritual movement raised banners decrying human rights abuses in China.

With files from The Canadian Press