He has netted 11 times in 35 international outings and becomes Bolton's sixth signing of the summer transfer window following the arrivals of Sean Davis, Paul Robinson, Sam Ricketts, Zat Knight and Chung-Yong Lee.
Klasnic is unlikely to be joined by Diomansy Kamara however, with reports linking the Fulham striker with a loan move to the Reebok Stadium believed to be wide of the mark.
Kamara joined the Cottagers from West Brom in 2007 but has managed a return of just nine goals in 40 appearances.
Despite three years remaining on his current contract, the 28-year-old has been a bit-part player since rupturing his cruciate knee ligament while playing for Senegal against Liberia in June 2008.
Bolton insist they know nothing of a deal for Kamara and that the link is mere speculation.
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