Devout regulars attending Athens's main Roman Catholic church that honours a first-century saint have discovered a 21st-century update: their donation box is now hooked up to a digital payments system.

The addition of the Point of Sale (POS) device in the Cathedral Basilica of St Dionysius the Areopagite is the first in a Greek church, even though their use is common elsewhere, including in Africa.  

Such was the stir created in Orthodox-dominated Greece that cameras from national broadcasters were on hand Sunday, trained on the POS's small screen — even though it was not yet switched on. 

The unit was expected to be working within a week, accepting card-tap donations as small as one cent, up to a limit of 1,000 euros ($1,130).

It was sitting on a wooden furniture unit alongside prayer candles that could be exchanged for donations.

"The first church donation box with POS: Tourists requested it, the Church made it happen," said an article on the protothema.gr news website.

The cathedral's priest, Georgios Dangas, noted mildly that churches elsewhere in the Western world had been using POS units for decades. 

"We have been asked to install a POS by tourists coming to Athens. Worshippers from all over the world who travel without cash want to give something for the church," he told AFP.

He added that the expenses of running the church, the salaries of the priests and the charity work are not paid by either the Greek state or the Vatican, so the contributions were vital.

Sunday mass in the church is frequently attended by women from the Philippines who work in the homes of the rich who live in nearby upscale neighbourhoods.

The POS device, which was hotly debated in Greece and on social media over the weekend, may find imitators in the Orthodox Church — the most followed religion in Greece. 

"The man who installed it told me that priests from Orthodox churches also contacted him. But they said let's see how it goes in the Catholic Church and then we'll see," the priest said.