"I met this morning with the entire first team squad and made it absolutely clear to all of them the responsibilities that come with playing for this club and the way they are expected to conduct themselves both on and off the pitch," said manager Rafael Benitez.
"The players worked extremely hard at last week's training camp, but we will take disciplinary action and fine any of them who are found to have breached club rules during our stay in Portugal. I've told the players this and they understand and accept the decision I have taken.
"Despite reports to the contrary, the spirit amongst the lads is very good with everyone looking forward to the game against Barcelona on Wednesday.
"We remain totally focussed on what will be a very tough game against the defending European Champions."