Shares of Japan Post jumped nearly 17 percent in the first day of trading after the company and its banking and insurance units raised a combined 1.44 trillion yen ($11.9 billion) in the world's biggest initial public offering of stock this year.

The long awaited sale of stock in the state-owned company is the biggest since Chinese e-commerce giant Alibaba Group Holdings raised $25 billion in its IPO in September 2014.

The Japan Post sale is meant to tease out some of the more than $14 trillion that Japanese investors have squirreled away in savings accounts. Some IPO funds will help pay for rebuilding from the 2011 tsunami disaster.

Japan Post Bank shares surged 15.4 percent and Japan Post Insurance shares soared 38.2 percent.