The People says they have been caught cavorting in a Brazilian nightclub.
One image shows Heitinga, 27, dancing suggestively with a mini-skirted blonde while swigging from a can of lager. Meanwhile 30-year-old Kuyt is seen in another picture with two local beauties - one blonde, the other brunette - draped around him.
The players went on the lash on Thursday after returning to Rio following their game against Uruguay in Montevideo.
Holland coach Bert van Marwijk fumed: "I told the players that they were now on holiday - but they ought to be aware of their responsibilities.
"I am convinced nothing indecent took place, but I don't understand why the players did what they did.
"They acted unwisely. It had been a very good tour until then - but this has tarnished it."
Heitinga insisted: "I was only trying to dance the samba.
"You can't just stand still to the beat.
"Of course we have a role as ambassadors, so we are furious some idiot with a camera found it necessary to post the pictures on the internet.
"It is all a big fuss about nothing. It looks much worse than it actually was.
"Luckily my wife has been very cool about it all."
Kuyt added: "This is annoying for our women, but nothing really happened - despite everything that has been suggested.
"It looks different when you see the pictures. But women were coming up to me, and I was gently pushing them away."