(REUTERS) -- Sweden said on Monday it had not added to its gold reserves in January, even though data from the International Monetary Fund on Monday showed a sharp rise in Stockholm's bullion holdings. 

A spokeswoman for the Riksbank said the central bank's gold holdings were unchanged at around 125.72 tonnes in January, while the IMF's monthly international finance statistics report showed an 18.3-tonne increase. 

We don't know what has happened, the spokeswoman said, referring to the discrepancy in the figures. 

This would have been Sweden's first increase in reserves in 2-1/2 years, when the central bank completed 36.6 tonnes in sales from 2007 to 2009, under the international Central Bank Gold Agreement by which signatories limit their collective sales of gold to 400 tonnes a year. 

The IMF data showed Kazakhtstan raised its gold holdings for the sixth time in 12 months, while Belarus added around 5 tonnes to bring its holdings to 42.64 tonnes and Mexico, a major buyer in 2011, cut its reserves by 0.16 tonnes to 105.85 tonnes.