It's not only the leaders who feel the strain at marathon talks on solving some of the world's most pressing problems.

As a summit of the Group of Eight rich nations entered a third day on Wednesday, the legions of security guards, smiling hotel staff, interpreters and journalists were also feeling the strain.

Japan clamped tight security down around the luxury hotel in the northern spa resort of Toyako where the leaders huddled, setting up roadblocks and preventing demonstrators from marching to the venue.

Even at the huge media centre built specially for the summit in the car park of a ski resort lodge 25 kilometres away from the summit venue, there were rigorous security checks - with a smile - for the 4,000 visiting journalists.

But as the summit entered the final furlong, fatigue was starting to show.

"Everyone feels tired," said one security guard as he laboured up a steep slope.

"This is the last day, finally,” he added.

More than 20,000 police have been called up from across Japan for the event, supported by private security guards.

But for Mitsugu Kubo, a 25-year-old private security guard cruising around on a Segway two-wheel motorised scooter, the main job has been to pose for photographs with foreign journalists.

"Compared with patrolling on foot, we have better mobility on this and can spot something suspicious more easily from up here," he said.

"We hope we have contributed to the environmentally friendly theme of the summit with these scooters," Kubo said.