(Adds analyst comment, detail)
ZURICH, May 7 (Reuters) - The Swiss National Bank's (SNB) foreign exchange reserves saw their first monthly fall of 2015 in April, suggesting the central bank may have held off on buying significant amounts of euros in a bid to weaken the Swiss franc.
Switzerland's central bank held 521.888 billion Swiss francs ($570.56 billion) in foreign currency at the end of April, preliminary data calculated according to the standards of the International Monetary Fund showed on Thursday.
This is slightly lower than the 522.399 billion francs recorded in March, which was revised from an originally reported 522.323 billion.
"This means mostly that the bank has not intervened massively to weaken the currency in the last month," IG Bank analyst Laurent Bakhtiari wrote in a note.
A spokesman for the SNB declined to comment on the fall.
In recent months, the SNB's board members have repeatedly stressed that the central bank sees Switzerland's currency as significantly overvalued and that it is prepared to intervene in the foreign exchange market if necessary.
Switzerland's central bank shocked financial markets in January by scrapping a more than three-year-old cap on the franc against the euro, sending the Swiss currency soaring and sparking fears for the country's export-reliant economy.
The Swiss franc has pared some gains in the months since the policy move amid speculation of SNB intervention in the foreign exchange market to weaken the safe-haven currency.
Fluctuations in the currency market can also affect the size of the SNB's foreign exchange holdings.
($1 = 0.9147 Swiss francs) (Reporting by Joshua Franklin and Paul Arnold; Editing by Gareth Jones)