About 25,000 protesters on Sunday surrounded Japan's Diet building to express strong opposition to Prime Minister Shinzo Abe's efforts to ram through a series of security-related bills that are considered unconstitutional by legal experts.

Calling him "Abedolf", they likened Abe to Adolf Hitler, saying he has behaved like a dictator and would drag Japan into armed conflict again if the bills pass in the current legislative session of the Diet.

The bills are a pet project for Abe, who says Japan can no longer shy away from its responsibility to help safeguard regional stability and must step out from under the security umbrella provided by the United States.