After win, Shinzo Abe calls for debate on Japan's constitution

An emboldened Shinzo Abe called on Monday for debate on Japan's pacifist constitution, which he said it was his "duty" to revise after scoring a strong win in weekend elections.

Voters backed the hawkish prime minister, despite a lacklustre economic performance, handing his Liberal Democratic Party and its allies control of more than half of the upper house of parliament.

Analysts say with the support of small nationalist parties, Abe may now have the numbers to push through a change to the constitutional bar on Japanese troops waging war.

"We have always set a goal of revising the constitution...That is my duty as president," Abe said.

"But the party does not have more than two-thirds of seats in both chambers by itself, so I don't expect the draft would pass as it is," he said, referring to the parliament's lower house as well, and suggesting compromise was needed.

"So I hope debate will steadily deepen."

Japan's constitution, imposed by occupying United States forces after World War II, prohibits the use of aggression to solve international conflicts.

The provisions are popular in the public at large, but reviled by rightwingers like Abe, who see them as outdated and punitive.

The LDP's own draft amendment plan calls for keeping the war-renouncing spirit of the constitution, but wants to remove language it sees as infringing on the country's means to defend itself.

Unofficial results from Sunday's vote compiled by media show the LDP and its Buddhist-backed allies, Komeito, now occupy more than half - at least 147 - of the seats in the upper chamber of parliament.

Full official results are expected on Tuesday.

With backing from fringe parties that also favour consitutional change, Abe could now have the two-thirds majority that he needs in both houses to push through any proposal to amend the country's basic law.

However, observers point out that corralling support for a revision from its coalition partner Komeito which has traditionally shied away from nationalist posturing could be difficult.

And the proposal would still face a referendum, with pollsters saying the vast majority of the public are wary of any softening of the country's pacifist stance.