By Jamie McGeever

LONDON (Reuters) - Financial markets, particularly equities, may be under-pricing the risk of Britain leaving the European Union, the world's largest asset manager said on Thursday, two weeks before Britons vote in a referendum on EU membership.

Owen Murfin, co-lead manager for global bond strategies at Blackrock <BLK.N.>, said that markets appear to be treating the possibility of Brexit as a local event rather than a globally systemic risk.

"There might be a little bit too much complacency. I would think that Brexit probably should be seen, in the context of the near term, as a bigger deal," Murfin told reporters at the firm's fixed-income outlook briefing in London.

"We've got to be careful ... and with equity markets very close to their highs I think it's a sensible time to take a bit of risk off, because the outcome is very uncertain," he said.

The S&P 500 <.SPX> is near a record high, and even Britain's FTSE 100 <.FTSE> is outperforming its European and Japanese peers this year.

New York-based BlackRock oversaw $4.7 trillion in assets globally as of March 31. Of that, $1.5 trillion was in fixed income assets.

A British vote to stay in the EU could lead to a recalibration of the country's interest rate outlook, with rates and yields likely to move up to be more in line with their U.S. equivalents, Murfin and his colleagues said.

Overall, ultra-low bond yields, interest rates and returns are fast becoming the main concern for investors.

Some $10 trillion of sovereign bonds carry negative yields, according to Fitch Ratings, and global yields as measured by U.S. bank Citi reached a record low this week, dragged down by a decline in Germany's benchmark borrowing costs to a new low of 0.03 percent.

"Interest rates are really starting to bite. Cash is now expensive. Cross-border flows are being driven by 'how do I get away from negative yields'," said Stephen Cohen, global head of fixed income beta at BlackRock.

"As rates go lower and curves go flatter, finding yield by extending duration is clearly running out of steam," he said.

Commerzbank, one of Germany's biggest lenders, is examining the possibility of hoarding billions of euros in vaults rather than paying to park it with the European Central Bank, according to sources familiar with the matter.

Such a move by a bank part-owned by the German government would be one of the most substantial protests yet against the ECB's ultra-low rates, which have been criticized by politicians including Finance Minister Wolfgang Schaeuble

Murfin and Cohen said investment-grade bonds and U.S. mortgage bonds are among the most attractive areas to invest for yield, and shorter-dated European bonds are a good proxy for negative-yielding cash.

Cohen said BlackRock has "ridden the wave" of rising U.S. Treasury prices in recent months but with yields now so low he's taking a more "cautious" view on the world's most important sovereign bond market.

On Thursday the 10-year U.S. yield fell to 1.668 percent <US10YT=RR>, the lowest since February, as investors continue to reduce bets on the Federal Reserve raising rates any time soon.

(Reporting by Jamie McGeever; Editing by Larry King)