Thursday's heavy rain failed to douse the rage of thousands of demonstrators who gathered in front of the Diet building in Tokyo to protest the controversial security legislation that is expected to pass by week's end.

They sang, drummed and yelled in the rain as the Diet edged closer to enacting the bills, which would allow the Self-Defence Forces to come to the aid of an ally, even if Japan itself is not under attack.

"I thought now is the last chance to raise my voice for the future of Japan, otherwise I would regret it for years to come," said a woman in her 40s from Tokyo's Itabashi Ward, who was protesting for the second consecutive day.