"It's correct that Fredrik has taken the decision to quit. I got the decision on Wednesday," Lili Assefa told the SVT channel.
The 35-year-old, capped 75 times by his country, was without a club after terminating his contract with Japan's Shimizu S-Pulse by mutual consent in February.
Ljungberg, also known for modelling Calvin Klein underwear and his colourful haircuts, made his name in England at Arsenal, where he won two Premier League titles between 1998 to 2007.
The attacking midfielder was also part of Arsenal's famed "Invincibles" who went unbeaten in winning the 2003-04 title.
Ljungberg subsequently joined West Ham United before spells in Major League Soccer, Scotland and Japan.
He appeared at two World Cups and two European championships before retiring from international football in 2008.