Barcelona, who finished runners-up in the Primera Liga, will not renew defender Reiziger and midfielder Cocu's contracts which expire at the end of the season, the club's director of football Txiki Begiristain said in a statement.
Kluivert and Overmars still have a year to run on their contracts but Barcelona said the two forwards were free to move on, while Turkish international goalkeeper Rustu Recber is also expected to leave the club.
Barcelona confirmed they had agreed to sign Brazilian defender Juliano Belletti from Villarreal on a four-year contract and said they were interested in recruiting Germany midfielder Michael Ballack from Bayern Munich.
Barcelona said they were still negotiating with another Netherlands international, Edgar Davids, and that Dutch defender Giovanni van Bronckhorst, signed on loan from Arsenal last year, would be staying at the club.
All six Dutch players mentioned are in coach Dick Advocaat's provisional Euro 2004 squad.
Begiristain said Barcelona had made what they believed was a fair offer to Cocu, who spent six seasons at the club, but that he had rejected it.
"We wanted to keep Cocu but we have to stick to our position," he said. "We must keep a cool head and not change the pay structure we have set."
Begiristain said Belletti would replace Reiziger, who stayed at Barca for seven years.
Begiristain added that Kluivert, who missed much of last season through injury, felt he was being "judged" by Barcelona fans each time he touched the ball.
"This is not good for him, nor for us nor his team mates," he said.
Begiristain said Barcelona had "real interest" in signing Ballack.
"We are aware of Ballack's intention to leave Bayern Munich. If that is confirmed, it would make it easier for us to begin negotiations with his club," he said.
On Davids, whose signing on loan from Juventus in January coincided with a marked improvement in Barcelona's form, Begiristain said Barcelona had made him an offer.
"We may know this week if we can reach an agreement or not. ... We know he has offers (from other clubs)," he said.
