(Bloomberg) -- Poland’s central bank intervened on the currency market for the first time in years, selling zloty, according to two people with direct knowledge of the transactions who asked not to be named because they’re not authorized to speak publicly.

The zloty weakened as much as 1.7% against the euro in thin, end-of-year trading. Earlier in December, the it touched the strongest level against the European currency in three months, as traders ignored repeated warnings from the central bank that the zloty should weaken to help the Polish economy recover.

The central bank’s press office declined to comment on Friday. For the last three months, the bank’s statement after its policy meetings noted that: “The pace of recovery may also be reduced by the lack of a visible and more durable zloty exchange rate adjustment to the global pandemic-driven shock and to the monetary policy easing introduced by the National Bank of Poland.”

“This may be a warning to shot that the NBP is monitoring the zloty and they don’t want it to gain too much,” said Piotr Matys, a currency strategist at Rabobank in Warsaw. “Perhaps they are afraid that domestic demand will not be too strong and the burden will be on exports as the main engine of economic growth.”

The zloty traded at a one-month low of 4.4885 against the euro, down 1.1% on the day, at 4:05 p.m. in Warsaw. The last time the central bank admitted that it intervened on the currency market was in 2013, when it sold foreign currency in a bid to strengthen the zloty.

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