Japan's controversial state secrets law came into effect Wednesday as hundreds of demonstrators took to the streets, saying the measure undermines the public's right to know and demanding that it be scrapped.

More than 300 protesters, including roughly 100 journalists, gathered in front of the prime minister's office in Tokyo's Chiyoda Ward, chanting slogans like "We oppose the secrecy law for going to war" and "Information belongs to citizens."

"We've seen more and more pressure on media organizations that are critical of the administration," said Seigo Arasaki, who heads the Japan Federation of Newspaper Workers Unions, known as Shimbun Roren. "We will monitor how the law will be applied, and raise questions,."