TOYAKO  - More than 20,000 police on Sunday sealed a secluded mountain resort in northern Japan as the world's top leaders gathered, with protests kept far away from the summit venue. Japan imposed a no-fly zone across a stretch of its northern island of Hokkaido as US President George W Bush arrived for three days of talks with 22 other leaders in the remote lakeside town of Toyako. Hundreds of activists held demonstrations for a second straight day in Sapporo, the closest major city to the summit area, on issues ranging from labour rights to Tibet to global poverty. Four Japanese nationals - three demonstrators and one television crew member of the Reuters news agency - people were arrested during the anti-G8 demonstration, police said Sunday. The protests were mostly peaceful, although police shattered the windows of a van that refused to stop as it went through traffic. "Down with the G8 summit" chanted some 100 demonstrators from left-wing labour unions, who were nearly outnumbered by riot police with helmets and shields. No arrests were immediately reported Sunday. A day earlier, police arrested three demonstrators and a cameraman accused of kicking officers. Activists of British-based charity Oxfam dressed up in oversized masks of the G8 leaders held up a mock cheque offering $50b for poor countries - a promise made at the summit in Scotland in 2005. Filipino activist Renato M Reyes, Jr said that he and his colleagues were trailed across Hokkaido by police, with some even sleeping in their car outside of the demonstrators' hotel. "There are so many police officers, asking for your licence, where you are going and what you are up to," said Reyes, Secretary-General of Bagong Alyansang Makabayan, an umbrella group of farmers, students and workers. He described it as "harassment."