Tsipras blamed European partners and the European Central Bank for forcing Greece's hand but said that would not halt the plan to hold a referendum next Sunday.

"(Rejection) of the Greek government's request for a short extension of the programme was an unprecedented act by European standards, questioning the right of a sovereign people to decide," Tsipras said in televised address to the nation.

"This decision led the ECB today to limit the liquidity available to Greek banks and forced the Greek central bank to suggest a bank holiday and restrictions on bank withdrawals."

He did not give details on how long banks would be shut or the restriction on the movement of capital.

Tsipras also said he sent a new request for an extension of Greece's bailout - which expires on June 30 - to leaders of euro zone countries and the heads of the ECB, the European Commission, the EU parliament and the EU Council.

"I am awaiting their immediate response to a fundamental request of democracy," he said, adding that such a move could prompt the ECB to turn on the liquidity tap again.

"One thing is clear: the refusal of a short extension, and the attempt to nullify a democratic procedure is an act deeply offensive and shameful for the democratic traditions of Europe.

Earlier on Sunday, the ECB froze the level of emergency funding available to Greek banks, which have seen a surge in withdrawals over the weekend after Tsipras called the referendum.

Tsipras said bank deposits and wage and pension payments in Greece remained safe and appealed to Greeks to stay calm.

(Reporting by George Georgiopoulos and Michele Kambas, Writing by Deepa Babington; editing by Anna Willard)