Fresh off a decisive election victory, Prime Minister Shinzo Abe pledged Monday to tackle what he called Japan's two national crises: the military threat from North Korea and an aging and shrinking population.

Abe said at a news conference that he is committed to protect the Japanese people's prosperity and peace from any contingency. He also referred to Japanese people who were abducted years ago and are believed to still be held by North Korea.

"I will pursue decisive and strong diplomacy to tackle North Korea's missile, nuclear and abduction issues and put further pressure to get it to change its policy," he said.

His ruling coalition was returned to power in elections for Japan's more powerful lower house Sunday.

Abe said Japan's decreasing population and aging is "the biggest challenge" for his Abenomics policy aimed at Japan's economic recovery from deflation. "The problem is progressing by the minute, and we cannot afford waiting around."

He promised a comprehensive package by the end of the year to deal with Japan's demographic challenges, including investments in education, productivity improvements and pension system reform.

Abe's Liberal Democratic Party and a small coalition partner together secured at least 313 seats in the 465-member lower house, passing the 310-barrier for a two-thirds majority. Three seats remained undecided.