Maxima's father was an associate of the notorious Videla regime

But the response far exceeded predictions.

"Seeing that we registered three billion calls, we reckon there may have been a deliberate attack", said KPN spokesman Brad Oudshorn.

One hundred people had been selected to chat online with the royal couple about their 2 February wedding, while others were permitted to log on and watch the exchange.

In the opening minutes of the session, however, screens across the country went blank.

Correspondents say it is not immediately clear who caused the crash or whether it was intended as a political protest.

They say the prince's relationship sparked controversy last year when it emerged that Miss Zorreguieta's father had been a civilian minister when Argentina was ruled by the military between 1976 and 1983.