BRUSSELS, Mar. 24 -- Belgium's Nyrstar (NYR.BR: Quote), the world's biggest producer of zinc, said it would launch an offer of five-year bonds, aiming to raise at least 100 million euros ($134.8 million) to fund further expansion into mining.

The company said in a statement released on Tuesday that the bonds would bear interest at an annual gross rate of 5.5 percent, and would be offered via a public offering in Belgium and Luxembourg.

KBC Bank and ING Belgium had been appointed as joint lead managers and as underwriters for the offering.

"The proceeds from the issue will further diversify our funding sources and will ensure that we continue to maintain the necessary financial strength to deliver our strategy,", Chief Financial Officer Heinz Eigner said in a statement.

Nyrstar is expanding into mining to complement its smelting operations, and has already bought mines or acquired stakes in them in the United States, Peru and Greenland.

The offer period would start on Wednesday and end on April 7, although early closing was possible, the statement said.