The world's central bankers are in "close communication" ahead of the U.K.'s referendum on membership of the European Union next week, according to Bank of Japan governor Haruhiko Kuroda, and stand ready to stabilize markets if voters back a British exit.

Kuroda, who warned on Thursday that fears over "Brexit" have already led to Japanese government bond yields falling to record lows, is the latest in a stream of central bankers warning of the potential effects of Brexit on the financial markets.

His comments come after Federal Reserve Chair Janet Yellen said the referendum had been taken into account in Wednesday's decision not to raise interest rates this month.

Although the Fed's statement did not mention the June 23 vote, Yellen warned in her press conference that the U.K. decision could "have consequences for economic and financial conditions in global financial markets." She added that it "could have consequences in turn for the U.S. economic outlook."

The Swiss National Bank decided to leave interest rates unchanged at minus 0.75% at its latest quarterly meeting on Thursday, saying it would defend the franc against rapid rises, and took the opportunity to talk of a possible Brexit as a risk.

"The imminent U.K. referendum on whether to stay in the European Union may cause uncertainty and turbulence to increase," it said.

Meanwhile in Frankfurt, the European Central Bank pointed to the referendum as among the downside risks relating to developments in the global economy, although it also cited the eventual normalization of U.S. interest rates, the slowdown of the Chinese economy and a low oil-price environment.

In Britain itself, Bank of England governor Mark Carney hit back at Brexit campaigners accusing him of breaking the rules of silence that unelected public officials are supposed to observe ahead of the referendum.

Carney was criticized in a letter from member of parliament Bernard Jenkin and told he "needs to be very careful what he says", but Carney counter-attacked, warning that Jenkin's position "demonstrated a fundamental misunderstanding of central bank independence."   As well as being a leading Brexit campaigner, Jenkin is chairman of the House of Commons'  committee of lawmakers on public administration and constitutional affairs.

The Bank of England says it has no view on the debate, but has a duty maintain monetary and financial stability and its published assessments have shown it believes leaving could trigger a recession.

"All of the public comments that I, or other Bank officials, have made regarding issues related to the referendum have been limited to factors that affect the Bank's statutory responsibilities and have been entirely consistent with our remits," Carney wrote.

The Bank of England Monetary Policy Committee's notes will be published later on Thursday and are expected to record members' comments on the risks to the economy.