Ryanair has said that it will allow Greek customers to pay with cash after capital controls caused problems with credit card payments on its web site. 

The imposition of capital controls on Sunday evening means Greeks are no longer able to purchase goods or services from many big international online suppliers including Google, Apple and Facebook. 

The airline, which operates out of 11 airports in Greece, said in a statement it was experiencing "high rates of decline" on their credit/debit cards. 

"Ryanair has now provided the option for Greeks looking to travel to buy their plane tickets in cash at the Ryanair ticket desk at its airports," the statement said.

Rival Easyjet, which also usually sells its tickets online, said Greek customers could book flights if their cards worked but declined to say if it was considering other measures to enable them to pay.