By Ira Iosebashvili, Rebecca Howard and Anjani Trivedi 

HONG KONG--The British pound rose sharply against the U.S. dollar Friday and hit its highest levels in years against the euro and yen as early results from Scotland's independence referendum suggested support for the pro-union campaign.

Five districts representing just 3.7% of the total vote have reported cumulative results showing a vote against independence, although a final national tally isn't expected until early Friday in Scotland. The pound was recently at US$1.6495 in Asia. Hong Kong-traded shares of HSBC, which has strong links to the U.K., rose more than 1%.

"It's a news flow driven thing right now; no one is watching technical levels," said Sacha Tihanyi, senior currency strategist at Scotiabank in Hong Kong. Mr. Tihanyi says the pound could hit $1.66 over the course of the day.

Many investors believe a vote against independence will remove an obstacle that has impeded the pound's rise against major currencies. In July, the pound hit its highest level against the dollar since the financial crisis, but then declined more than 6% to a 10-month low, a selloff driven partly by the rising popularity of Scotland's independence movement. In recent weeks, many investors have come around to the view that Scottish voters would choose to remain in the U.K., giving the currency a lift off the lows.

A vote to stay in the U.K. "would remove uncertainty over some very big issues," said Alan Ruskin, global head of G-10 foreign-exchange strategy at Deutsche Bank. The pound "can now revert back to the traditional fundamentals which had been driving it, such as the relative strength of the U.K. economy and expectations of tightening by the Bank of England," Mr. Ruskin added.

In a survey conducted by pollster YouGov, 54% of respondents voted against Scotland exiting the U.K., compared with 46% who supported independence. YouGov said the survey was based on recontacting voters after they voted. It was released about 30 minutes after polls closed at 10 p.m. U.K. time.

The movements in the pound came in a busy currency trading session in Asia, with the yen sliding to a six-year low against the dollar. It was at $109.23. The euro was also under pressure on concerns the European Central Bank would resort to more drastic stimulus measures.

In the run-up to Thursday's vote, investors had expressed concerns about what currency regime an independent Scotland would adopt, as well as how the two countries would divide up debt and natural resources. These worries weighed on the pound, helping to thwart a rally driven by the belief that the Bank of England would be one of the world's first central banks to raise short-term interest rates since the financial crisis, putting it more or less on even footing with the Federal Reserve.

Economic data point to strong growth in the U.K., and have served to underscore the country's divergence with Europe and Japan. The European Central Bank surprised investors earlier this month with an unexpected rate cut, while many investors expect the Bank of Japan to continue its easy-money policies as it tries to kick-start economic growth.

Higher rates boost the appeal of a currency--and assets denominated in that currency--for money managers.

With the BOE getting ready to tighten monetary policy while other central banks continue to ease, "the pound is likely to be one of the better-performing major currencies, in the medium term," said Marc Chandler, a strategist at Brown Brothers Harriman.

The bulk of those gains likely will come against currencies such as the euro, rather than the dollar, as the Fed also is expected to begin raising interest rates next year, Mr. Chandler said.

The euro was down against the pound, buying 78.26 pence

Write to Ira Iosebashvili at ira.iosebashvili@wsj.com and Rebecca Howard at rebecca.howard@wsj.com