Details from the Washington Post:

A decision to close banks on Monday was a sign that Greece’s half-decade battle to stay on the shared euro currency may swiftly be coming to an end. ATMs in Athens were running out of money, and tensions were running high Sunday as Greeks stood in line for hours to scrape together petty cash for basic supplies. Lines mounted at gas stations as worried residents topped off their tanks for what could be a period of time in a cashless nation.

Here is the statement from Greece prime minister Alexis Tsipras: