The 24-year-old Swede has built up a solid reputation in the Dutch top flight since joining NEC from Landskrona BoIS in 2003, and is reportedly a target of English Premier League trio Newcastle, Bolton and Fulham.
NEC technical director Carlos Aalbers admitted the transfer talk comes as no surprise, but added that there was no movement behind the scenes as yet.
"The clubs have not officially contacted us yet," Aalbers told Voetbal International magazine. "Jonas has made a big development, so the interest in him doesn't surprise me.
"He still has a contract until the summer of 2009, though, so only when we receive a really good offer will we be open for a transfer."