PSV sign Slovenia striker Matavz
The 22-year-old, who scored 32 goals in 69 league matches for Groningen, has played nine times for his country including an appearance at last year's World Cup in South Africa.
Former Russia striker Dmitry Bulykin has joined Ajax Amsterdam on a one-year deal after leaving Anderlecht as free agent, the Dutch champions said.
The 31-year-old was prolific last season on loan at ADO Den Haag, scoring 21 goals in 30 league matches.
Twente Enschede have signed 21-year-old Feyenoord midfielder Leroy Fer on a three-year deal for five million euros, the club said on their website.
The Netherlands Under-21 player made his debut aged 17 in 2007 and played 103 league games for Feyenoord scoring 14 goals.
Feyenoord have themselves captured Sweden Under-21 striker John Guidetti, 19, on a one-year loan deal from Manchester City, the club said on their website.
They have also added Dutch playmaker Otman Bakkal to their squad on loan from PSV Eindhoven. He was infamously bitten on the shoulder by Uruguay striker Luis Suarez in November.
Suarez, who was playing for Ajax Amsterdam before joining LIverpool in January, was handed a seven-match ban.