U.S. Federal Reserve Chairman Alan Greenspan is in communication with the Fed from an undisclosed location after his flight from Switzerland to Washington was diverted Tuesday morning following attacks that wreaked havoc in New York and Washington, the Fed said.

While Fed spokesman David Skidmore would not confirm the reports, Swiss police told Reuters that the Fed chief was still in Switzerland where he had attended a Bank of International Settlements meeting in Basel.

Separately, airline sources said that Greenspan had been on a Swissair flight from Zurich to the United States. The sources confirmed that the plane had turned around in flight and had returned to Zurich's international airport.

``His return flight was diverted today...he is working and in communication with the Federal Reserve,'' Skidmore said. He declined to give further details of Greenspan's location.

Skidmore added that could not say whether the Fed chairman was in touch with a group of major U.S. financial market regulators who said earlier on Tuesday that they had been in constant communication following the attacks.

The President's Working Group on Financial Markets is an ad hoc group designed to deal with issues that face the U.S. financial system. It consists of the U.S. Treasury Department, the Fed, the Securities and Exchange Commission and the Commodity Futures Trading Commission.

Earlier, the Fed and the European Central Bank said they stood ready to provide liquidity to ensure the proper functioning of financial markets.