Japan's ruling bloc enacted a law targeting conspiracies to commit terrorism and other serious crimes on Thursday, June 15, pushing it through parliament's upper house despite concerns over civil liberties, Reuters says.

The vote on the bill, which has divided the public, followed opposition party delaying tactics, protests and concerns raised by a United Nations expert - who called the legislation "defective" - and came days before the current session of parliament was set to end on June 18.

Japanese governments had tried three times previously to pass similar legislation, which officials say is needed to ratify a U.N. treaty aimed at global organized crime as well as to prevent terrorism as Tokyo prepares to host the 2020 Olympics.

"It's only three years until the Tokyo Olympics and Paralympics and so I'd like to ratify the treaty on organized crime as soon as possible so we can firmly cooperate with international society to prevent terrorism," Prime Minister Shinzo Abe told reporters. "That's why the law was enacted."

The legislation would criminalize plotting and preparing to commit 277 "serious crimes" that critics such as the Japan Federation of Bar Associations note include acts with no obvious connection to terrorism or organized crime, such as sit-ins to protest construction of apartment buildings or copying music.

Opponents see the legislation as part of Abe's broader to increase state powers and fear ordinary citizens could be targeted, despite government assurances to the contrary.

Opposition Democratic Party leader Renho, who goes by one name, in a statement blasted the ruling party tactics and termed the law "brutal" legislation that violated freedom of thought.

Combined with a widening of legal wiretapping and the reluctance of courts to limit police surveillance powers, the changes could deter grassroots opposition to government policies, critics say.

Critics say gathering information on possible plots would require expanded police surveillance, and the legislation has been compared to Japan's "thought police", who before and during World War Two had broad powers to investigate political groups seen as a threat to public order.

A Kyodo news agency survey last month showed voters are split over the bill, with support at 39.9 percent and opposition at 41.4 percent.