* Apple surge fuels gains for Nasdaq
* Volatility index VIX falls back after hitting highest since 2015
* Selloff had knocked more than $1.5 trillion off S&P (Updates to open)
Feb 6 (Reuters) - U.S. stock markets bounced after a torrid opening on Tuesday, bargain-hunters and gains for Apple pushing the tech-heavy Nasdaq and the Dow Jones Industrial Average into positive territory after two days of heavy losses.
Both the S&P 500 and the Dow sank more than 4 percent on Monday, their biggest falls since August 2011, as concerns over rising U.S. interest rates and government bond yields hit record-high valuations of stocks.
New York's three main indexes sank as much as 2 percent on the opening bell but they quickly moved back into positive territory.
An almost 2 percent gain for Apple was at the heart of an almost half percent gain for the Nasdaq Composite.
"Daily drops of 3 percent or more have been buying opportunities for the S&P 500 post financial crisis," said Lori Calvasina, head of U.S. equity strategy at RBC Capital Markets.
At 9:49 a.m. ET (1449 GMT), the Dow Jones Industrial Average gained 0.25 percent to 24,406.14. The S&P 500 rose 0.2 percent to 2,654.25 and the Nasdaq 0.4 percent to 6,993.47.
(Reporting by Tanya Agrawal; Editing by Arun Koyyur and Patrick Graham)