Investors sent Japan Post stocks soaring in its long-awaited Tokyo trading debut Wednesday, while the announcement of a Hong Kong-Shenzhen trading connect boosted Chinese stocks.

Shares in the vast Japanese company -- along with its banking and insurance units -- were listed on the Tokyo Stock Exchange following an $11.5 billion share sale.

Japan Post Holdings' equities soared nearly 17 percent from a 1,400 yen IPO price, while its banking unit's stock jumped 16 percent from their offering price to 1,680 yen.

But the hotly anticipated insurance unit's offering was the early leader, skyrocketing 33 percent.

"There's a carnival atmosphere in the market," said Mitsushige Akino, executive officer at Ichiyoshi Asset Management Co. in Tokyo. "The prices were relatively cheap and the dividend yields are high."

Japan Post's IPO was the largest offering globally since Chinese e-commerce giant Alibaba's record $25 billion debut last year.

The benchmark Nikkei 225 index enjoyed a 2.22 percent surge by 0230 GMT.

Shares in Japanese airbag maker Takata slumped on Tuesday after US auto safety regulators announced a record $200 million civil fine against the firm for providing inadequate and inaccurate information about its dangerously explosive safety devices.

Takata shares fell 10.71 percent to their lowest point since August in Tokyo trading.

In Hong Kong and Shenzhen, Chinese stocks rallied following an announcement by the head of China's central bank that a trading link between the two southern Chinese cities will start this year.

The Hang Seng had gained 2.86 percent by 0215 GMT, while the Shenzhen Composite Index rose 2.26 percent.

But Ronald Wan, chief executive officer of Hong Kong-based Partners Capital International, sounded caution after the mixed fortunes of a similar scheme linking Hong Kong and Shanghai markets.

"Optimism may wane soon, given what has happened to the Hong Kong-Shanghai connect. Regulatory investigations into the financial industry, as well as weak confidence in mainland stocks, may keep investors away."

China sent its clearest signal yet that the world's second-largest economy would lower its growth targets on Tuesday, with President Xi Jinping saying annual expansion of only 6.5 percent would be enough to meet its goals.

- Oil boost for Malaysia -

In currency markets, Malaysia's ringgit strengthened 0.66 percent against the US dollar Wednesday, boosted by resurgent oil shares on Wall Street as Asia's only major net oil exporter.

There was a more mixed picture in early Asian trading with US benchmark West Texas Intermediate for delivery in December up two cents at $47.92 while Brent crude for December traded two cents lower at $50.52 a barrel at around 0225 GMT.

"Higher oil prices and positive risk sentiment resulting from higher US equities fuelled the ringgit's gains," said Sim Moh Siong, a foreign-exchange strategist at Bank of Singapore.

Wall Street stocks rose for the second straight session Tuesday, led by oil and retailers after a pair of US clothing chains raised their earnings forecasts.

Elsewhere the Korean Won and Thai baht also enjoyed a boost, with Thailand's central bank projected to keep key rates on hold at a review Wednesday.

The dollar was trading at 121.20 Japanese yen, up from 121.03 in late US trade on Tuesday.

The euro was at $1.0949 from $1.0959 and at 132.68 yen from 132.64 yen.