ATHENS — Prime Minister Alexis Tsipras announced Sunday night that Greece’s banks would be closed as of Monday, as the fallout from ruptured debt negotiations with the nation’s creditors began inflicting pain on ordinary people while raising alarm in Washington, Brussels and Berlin.

The emergency measures escalated the confused and unpredictable state of a crisis that some analysts say could ripple through global financial markets and undercut European unity. Most Asian markets opened lower on Monday.

With so much at stake, leaders in other capitals encouraged a continued search for a way to prevent Greece from being forced out of Europe’s currency union. Greece owes a large debt payment by the end of Tuesday, and has scheduled a referendum for next Sunday on whether to accept the terms of an offer from its creditors to release bailout aid it needs to meet its financial obligations.

Mr. Tsipras announced the emergency banking shutdown, which will also close the stock exchange, and imposed capital controls several hours after the European Central Bank said it would not expand an emergency loan program that had been propping up Greek banks for weeks. The banking system had neared insolvency after panicked account holders withdrew billions of euros, a pattern that continued over the weekend.