ATHENS: Greek banks and the Athens stock market will be closed on Monday and capital controls will be imposed, Prime Minister Alexis Tsipras announced, pleading for calm after anxious citizens emptied ATMs in a dramatic escalation of the country's debt crisis.

Take a look: Greece faces banking collapse as ATMs run dry.

In a statement, Tsipras on Sunday said the Bank of Greece had recommended a “bank holiday and restriction of bank withdrawals” after international creditors refused to extend the nation's bailout beyond its June 30 expiry date, sparking default fears over an IMF loan repayment due the same day.

Amid growing concern the country was headed for financial collapse and a possible eurozone exit, the European Central Bank said earlier on Sunday it would not increase its financial support to Greek banks.

In a bid to stave off panic, Tsipras said the Greek stock market would also remain closed on Monday and he added that Athens had again requested a “prolongation of the (bailout) programme”.

Urging calm, he assured Greeks their deposits, were “totally safe”.

“Equally safe is the reimbursement of salaries and pensions,” he said.

“Any difficulties that may arise must be dealt with with calmness. The more calm we are, the sooner we will get over this situation.” Uncertainty over how events will unfold in coming days prompted long queues of up to a hundred people to form outside some ATMs in Athens.

“I tried many machines – five, six, eight, ten – I am not sure,” said Voula, who was on the lookout for a working ATM in central Athens.

“I feel anxious, sad, angry about the government,” she told AFP. “They put Greece on a very dangerous adventure.” Since Friday night alone, 1.3 billion euros ($1.45 billion) have been withdrawn from the Greek banking system, according to the head of the bank workers' union Stavros Koukos.

A banking source in Greece said only 40 percent of cash machines now had money in them and a host of European governments including London and Paris advised citizens travelling to Greece to carry money with them.

US President Barack Obama and German Chancellor Angela Merkel also weighed in on Sunday, saying Greece needed to find its way back to a path of reform without exiting the eurozone.

In a telephone call about the unfolding crisis, Obama and Merkel “agreed that it was critically important to make every effort to return to a path that will allow Greece to resume reforms and growth within the eurozone,” the White House said.

The International Monetary Fund, a key creditor in the negotiations accused by Athens of pushing a hardline on reforms, said it was monitoring the unfolding crisis and was ready to provide assistance.

IMF Managing Director Christine Lagarde expressed disappointment that talks had broken down between Athens and its creditors, but said she believed the eurozone was in a “strong position” to respond to the crisis.

“The coming days will clearly be important,” she said in a statement.