Hundreds of protesters rallied under heavy police security Sunday in Japan as leaders from the top industrialized nations began arriving for their annual summit.

A morning protest ended peacefully. Another sponsored by leftist demonstrators was to be held later in the evening.

The rallies follow a demonstration by about 2,500 on Saturday that lead to a brief clash with police in which four people — including a television cameraman — were detained.

The protesters are demanding the Group of Eight be dissolved and urgent measures be taken to solve climate change and world hunger.

"Down with imperialism," said one large red banner carried at the front of the march.

Japanese police have been out in force to assure there are no incidents during the G-8 summit, which starts in Lake Toya, about 60 miles south of Sapporo city on Monday.

President Bush arrived at Lake Toya as the march was being held.

Protesters have not been able to get anywhere near the summit venue, but have scheduled daily rallies in Sapporo, the largest city on the northern Japan island of Hokkaido. They are often outnumbered by the riot police deployed to control them.

Japan has mobilized a staggering 20,000 police officers — primarily in and around the summit site but also in major cities including Tokyo — to avert any terrorist attacks. Coast Guard vessels and military helicopters have also been deployed.

Last year, tens of thousands of anti-globalization protesters demonstrated when the summit was held in Germany and some threw Molotov cocktails at police, who used water cannons and horses to drive them back.

The G-8 leaders represent the United States, Japan, Russia, France, Britain, Canada, Italy and Germany. They are being joined by African leaders and the leaders of China, India and other rapidly growing economies, making this year's summit the biggest ever.