(Updates market action; adds quote, background)

By Richard Leong

NEW YORK, June 23 (Reuters) - U.S. Treasury prices rose in late U.S. trading on Thursday, as early official results showed Britons supporting their nation to exit the European Union had a narrow lead, renewing safe-haven bids for lower-risk government debt.

With results in from the first 13 of 382 voting districts, those in favor of ending Britain's 43-year membership in the EU were on 52.4 percent of the vote, while those wanting to stay were on 47.6 percent. It was too early to establish a firm trend in a contest that remained too close to call.

Investors and policy-makers have worried that if Britain leaves the EU it would roil financial markets and harm the global economy, as such a move would lead to renegotiation of U.K. trade pacts and other countries.

Early surveys released shortly after U.K. polls closed showed the "Remain" camp had a decent lead over the "Leave" camp.

"It's going to be a longer night than expected," said Lisa Hornby, fixed-income portfolio manager at Schroders Investment Management in New York. "Treasuries are well bid. People are a little nervous.

"We still have a lot of results ahead of us," she said.

Benchmark 10-year Treasury notes were up 16/32 in price, with the yield at 1.684 percent, down 5.5 basis points from Thursday's closing level, Reuters data showed.

Earlier on Thursday, the 10-year Treasury yield touched a three-week high at 1.749 percent.

(Reporting by Richard Leong; Editing by Sandra Maler and Leslie Adler)