Japanese Prime Minister Shinzo Abe on Thursday pushed through legislation in the lower house of parliament that could see troops sent to fight abroad for the first time since World War Two, despite thousands of protesters overnight chanting and holding up placards reading "No War, No Killing."

A lower house panel approval on Wednesday of the unpopular bills, which would drop a ban on collective self-defense or fighting to defend a friendly country like the United States, sparked demonstrations and more are planned.

Polls show that about 80 percent of Japanese find the bills distasteful, and the majority of them say they think the legislation is unconstitutional

The bills will now go to the upper house, and if no vote is taken after 60 days they will be returned to the lower house, where Abe's coalition can enact them with a two-thirds majority.

Abe says a bolder security stance, welcomed by ally Washington, is essential to meet new challenges, such as those from a rising China.

"The security situation around Japan is getting tougher," Abe told reporters after the vote, which was boycotted by the main opposition parties. "These bills are vital to protect the Japanese people's lives and prevent war."

The changes expand the scope for Japan's military to provide logistics support to friendly countries, relax limits on peacekeeping operations and make it easier to respond to "grey zone" incidents falling short of war.

Opponents say the revisions could entangle Japan in U.S.-led conflicts around the globe and violate pacifist Article Nine of the U.S-drafted, post-war constitution.

China's Foreign Ministry said the move called into question Japan's post-war commitment to "the path of peaceful development", and urged Japan to learn the lessons of history.

Sino-Japanese ties have long been frayed by China's memories of Japan's wartime aggression, although relations have thawed since a November leaders' meeting.

Abe, who returned to office in 2012 pledging to bolster Japan's defenses and reboot the economy, has seen his support slip to around 40 percent on voter doubts about the legislation and other policies, such as a plan to restart nuclear reactors.

A clash with the governor of Okinawa over a U.S. Marines air base will likely flare up in August, when Abe will also unveil a controversial statement marking the 70th anniversary of the end of World War Two.

Some analysts have begun to draw parallels to Abe's grandfather, Nobusuke Kishi, a wartime cabinet minister who was premier from 1957 to 1960 and resigned on July 15, 1960 because of a public furor over the U.S.-Japan security pact.

Reuters