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,.”

Under the law that cleared the Diet in December 2013, the heads of 19 government ministries and agencies can now designate as state secrets information deemed to be sensitive in the areas of diplomacy, defense, counterterrorism and counterespionage.

A recent Kyodo News survey covering the 19 government offices showed the number of state secrets will likely be around 460,000.

Civil servants or others who leak the secrets will face up to 10 years in prison, and those who instigate leaks, including journalists, will be subject to a prison term of up to five years.

Prime Minister Shinzo Abe, who established the National Security Council to speed up decision-making on diplomacy and defense, has said the law will help Japan to promote exchanges of sensitive information with other countries and forge closer ties with them.

State secrets are defined in 55 categories, including information about the development of submarines, aircraft, weapons and ammunition. Intelligence and images obtained via radio waves and satellites and provided by foreign governments and international organizations could be withheld from the public.

The initial five-year-designation period for a state secret can be extended for up to 30 years. But state secrets can be classified for a maximum 60 years if approved by the Cabinet for security reasons.

The law takes effect just as Abe appears to be seeking greater influence over the nation’s media, according to Koichi Nakano, a professor of political science at Sophia University in Tokyo.

The LDP sent a letter to Japan’s five biggest broadcasters last month to demand “neutral” reporting on the election. Abe told reporters on Dec. 1 he didn’t order the party to send the letter, though he hoped the election would be covered “fairly and impartially.”

The Japanese Federation of Bar Associations said on its website the new act opens the door to the government arbitrarily designating secrets.

“The definition of secret is very vague, and people, including myself, are wary of misuse,” said Kaori Hayashi, a professor at Tokyo University’s Graduate School of Interdisciplinary Information Studies.

The Japan Newspaper Publishers and Editors Association said in a Dec. 8 statement the maximum sentence for leaks was too harsh and could damage reporting activities and the public’s “right to know.”

Criticism has also been directed at the absence of an independent watchdog, as oversight entities will be placed under government control.

To ease such public concerns, the Cabinet approved guidelines on the handling of state secrets, pledging that it will keep “the minimum amount of information as secrets for the shortest period of time possible” as the public’s right to know should be “greatly respected” in a democratic society.

“We will make sure that the people’s right to know will not be hurt,” Chief Cabinet Secretary Yoshihide Suga said on Tuesday.

It has been revealed, meanwhile, that the Cabinet Intelligence and Research Office, which holds jurisdiction over the secrecy law, had warned government offices in 2011 that people who have studied or worked abroad have a higher risk of leaking state secrets.

Under the secrecy law, security clearance is required for officials to handle state secrets, and the government will set up hotlines so officials can report suspicions about arbitrary classification or declassification of state secrets.

The prime minister is also required to make an annual report to the Diet on the designation, safeguarding and disclosure of state secrets.

After the passage of the secrecy bill last year, Japan fell six places to 59th out of 180 nations in Reporters Without Borders’ 2014 World Press Freedom Index, below such nations as Serbia and Botswana.

“Investigative journalism, public interest and the confidentiality of journalists’ sources are all being sacrificed by legislators bent on ensuring that their country’s image is spared embarrassing revelations,” the group said.