TOKYO — Prime Minister Shinzo Abe of Japan won a commanding majority for his party in parliamentary elections on Sunday, reported NHK, the public broadcaster, fueling his hopes of revising the nation’s pacifist Constitution.

NHK said that Mr. Abe’s governing Liberal Democratic Party and its allies had overcome challenges from upstart rivals to capture two-thirds of the seats in the lower house of Parliament. Final results will be delayed until later on Monday because a typhoon that battered Japan on Sunday prevented votes from being counted in 12 precincts. But with the majority of votes counted, the Liberal Democrats and their coalition partner had won enough seats to reach the two-thirds mark.

Pre-election opinion polls had shown lukewarm support for the prime minister’s policies and competition from a party founded by Tokyo’s popular governor, Yuriko Koike, as well as another new center-left party.

For Mr. Abe, the results were a vindication of his strategy to call a snap election a year earlier than expected, and they raised the possibility that he would move swiftly to try to change the Constitution to make explicit the legality of the Self-Defense Forces, as Japan’s military is known.