International wholesale telephone call carrier iBasis Inc said on Monday it has filed a lawsuit against its majority Dutch owner KPN to block a buyout offer.

Last week IBasis rejected KPN's offer to buy out the remaining 44 percent of the company for $48.2 million, or $1.55 a share, as being grossly inadequate. KPN had announced its cash tender offer on July 13.

IBasis's Nasdaq-listed shares were up 2.6 percent at $1.99 at 1732 GMT on Monday.

In a statement on Monday iBasis said it was seeking an injunction and other unspecified relief in Delaware Chancery Court.

A KPN spokesman said the company had no comment to make on the lawsuit.

IBasis provides wholesale access for telecoms companies for international and long distance calls, as well as prepaid calling services.

 (Reporting by Ben Berkowitz; Editing by Greg Mahlich)