TOKYO- Protesters gathered in front of the Diet building in Tokyo voiced outrage over a forcible vote on a controversial anticonspiracy bill into law in the early morning on Thursday.

"How could they do this?" a participant in the rally said in an angry voice, referring to the ruling bloc's use of an unusual procedural option to allow the full House of Councillors, the upper chamber of the Diet, Japan's parliament, to vote on the bill, without a prior vote by a related Upper House committee.

"That was an attempt to cover up the scandal involving the Kake Educational Institution," headed by a personal friend of Prime Minister Shinzo Abe, another protester argued.

The ruling bloc appears to be eager to close the ongoing Diet session on Sunday as originally scheduled, to fend off the opposition camp's grilling over the scandal.

On Wednesday night, thousands of citizens rallied before the Diet building for a last-minute protest against the bill, aimed at punishing those involved in conspiracies to commit serious crimes before such crimes are committed. The government insists that it is designed to prevent terror attacks.

Some opposition lawmakers joined some 200 remaining demonstrators in the morning following the enactment of the legislation in the Upper House. "The government's explanations were full of contradictions," one of them told the citizens.

"It's regrettable, but we have no time to be disappointed because we have to work to scrap the law," said Toshikazu Miyagawa, 68, from Tokyo's Sumida Ward.

Yoko Adachi, a 69-year-old former high school teacher from Nerima Ward, condemned the ruling coalition as abusing its parliamentary majority to push through the contentious bill.

"I'm worried that this may happen again," as Abe is keen to revise war-renouncing Article 9 of the constitution by 2020, Adachi said. (Jiji Press)