A group of Tokyo university students have staged a rare hunger strike in front of Japan's parliament as they protest against security bills that critics fear would drag the country into foreign wars.

The move highlights growing opposition to legislation backed by Prime Minister Shinzo Abe, just days after Japan's national bar association joined the effort to prevent the constitutionally pacifist nation from enacting changes that could see Japanese troops engage in combat for the first time since the end of World War II.

Four male students began their hunger strike on Thursday afternoon in front of the Diet building, saying a "direct and tough approach" was required to block the bills, which are being hotly debated in parliament.