Japan passed a controversial anti-terror law on Thursday that sparked street protests and warnings from critics that it would stomp on citizens' privacy rights and lead to over-the-top police surveillance.
Japan PM Shinzo Abe's ruling bloc pushed it through the upper house early on Thursday, despite vocal opposition.
The upper house of parliament passed the conspiracy bill early Thursday morning after a full night of debate by sleepy parliamentarians and unsuccessful efforts on the part of Japan's weak opposition to block it.
Thousands of demonstrators protested outside the legislature over the bill which criminalises the planning of serious crimes.
The government argues the law is needed to improve security ahead of the 2020 Olympics, and to comply with a UN agreement Japan has signed.
But critics say it weakens civil liberties and could be abused to monitor and target innocent citizens.
The bill, which criminalises the plotting and committing of 277 acts, is an amendment of Japan's existing law against organised crime syndicates.
It bans the procurement of funds or supplies, and the surveying of a location, in preparation of a crime.
An entire group - defined as two or more people - can be charged if at least one member is found to have been plotting a crime.