Shinzo Abe has taken office for a third term as Japan's prime minister, appointing a former military officer as his defence minister but keeping the other members of his previous cabinet.

Parliament re-elected Mr Abe after his Liberal Democratic Party won a renewed mandate in a December 14 snap election that the prime minister said was needed for him to carry out further economic and political reforms.

Mr Abe said economic recovery is vital to achieving his key policy goals such as stronger national security and carrying out the most drastic reforms of the economy since the Second World War.

"My commitment to protecting public safety, lives and happiness is unchanged," Mr Abe said in a late night news conference "We must, of course, deal with many issues, but nothing can be accomplished without a strong economy."

Gen Nakatani, the new defence minister, headed the Defence Agency in 2001-2002 under former prime minister Junichiro Koizumi, before it won fully-fledged ministry status. A graduate of the National Defence Academy, he attained a rank of first lieutenant before leaving the military.

Mr Nakatani favours a stronger role for the military, which is constrained by the country's commitment to pacifism under the constitution drafted by the American occupation forces following Japan's defeat in the Second World War.

Mr Nakatani said Mr Abe specifically asked him to tackle "national security in order to protect Japanese territory, the people's lives and properties."

He said: "This time I feel more strongly about my responsibility. Japan's security environment has changed, and we must fortify our national security."

Mr Abe favours revising the constitution as part of his effort to fortify Japan's military, after already revising policies to allow the defence forces to aid allies if they come under attack under a policy dubbed "collective self-defence".

Analysts said Mr Abe likely wants a stronger figure to help handle anticipated fierce questioning over defence-related issues in upcoming parliamentary debates.

"Of course, I will tackle various key policies other than the economy," he said, citing education, social welfare, reconstruction of disaster-stricken areas and revising the constitution.

"It is important for everyone to think about a constitution that is appropriate for 21st-century Japan. I believe that would be a first step towards building a new Japan," Mr Abe added.