Major Asia Pacific markets were mixed on Thursday as investors remained cautious over the fast-spreading new coronavirus that has infected more than 81,000 people and killed over 2,700.

Most of the people infected and killed by the disease to-date are from China. However, the number of cases outside the country has surged in recent weeks — especially in places like South Korea, Italy, and Iran. That's led to global sell-off, including in the U.S. where the S&P 500 wiped out $1.7 trillion in just two sessions.

Japanese stocks led losses among major markets in the region as the Nikkei 225 fell 2.13% to close at 21,948.23 while the Topix index ended its trading day 2.37% lower at 1,568.06. The Japanese yen, considered a safe-haven asset, traded at 110.13 versus the dollar, strengthening from levels above 111.00 earlier in the week.

In South Korea, the Kospi closed 1.05% lower at 2,054.89 as the Bank of Korea kept its policy rate unchanged. The central bank surprised markets by holding its benchmark interest rate at 1.25% when analysts polled by Reuters were expecting a cut. That was despite a recent spike in the number of infection cases in the country — jumping from around 31 to over 1,000 in a little more than a week.

Aberdeen Standard Investments' Leong Lin Jing described the Bank of Korea's interest rate decision as "a little bit curious."

"Bank of Korea has had a habit of being a little bit behind the curve … when acknowledging that growth is slowing down," Leong, who is Asian fixed income investment manager at Aberdeen, told CNBC's "Street Signs" on Thursday.

On Thursday, South Korea's Centers for Disease Control and Prevention confirmed 334 more cases, bringing the country's total to 1,595. South Korea now has the most number of confirmed cases outside China, where the outbreak was first reported.

Coronavirus live updates: South Korea reports surge of 334 more cases, bringing total to 1,595

The South Korean won weakened against the dollar to 1,215.27, from levels near 1,212 before the decision.

Hong Kong's Hang Seng index was largely flat, as of its final hour of trading. Hong Kong-listed shares of Standard Chartered jumped more than 1% despite the lender warning that recent headwinds like the coronavirus outbreak will likely result in income growth in 2020 being below its "medium-term 5-7% target range."

Mainland Chinese stocks, on the other hand, bucked the overall trend regionally as they saw gains on the day. The Shanghai composite rose 0.11% to about 2,991.33 while the Shenzhen component was up 0.32% to 11,534.02. The Shenzhen composite also advanced 0.24% to around 1,895.13.

The moves upward on the mainland came as the World Health Organization said Wednesday the number of daily new coronavirus cases outside China exceeded those inside the country for the first time.

In Australia, the benchmark S&P/ASX 200 closed 0.75% lower at 6,657.90 as shares of major banks in the country sold off.

Overall, the MSCI Asia ex-Japan index was 0.3% lower.

One investor told CNBC on Thursday that the markets were already "looking for an excuse" to sell.

"Everybody's just ready, everybody was saying we ... could have a fall back," Simon Fentham-Fletcher, chief investment officer at Freedom Asset Management, told CNBC's "Capital Connection" on Thursday.

"COVID-19 looks like it's an excuse," Fentham-Fletcher said, in reference to the official name of the coronavirus that has come under the spotlight. "The bears have been hanging around for awhile."

"This is a perfect, perfect excuse," Fentham-Fletcher said, adding that he thought the reaction was "slightly overblown"