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By Jan Lopatka
PRAGUE, April 14 (Reuters) - The Czech crown <EURCZK=> soared 7.9 percent to all-time highs in thin overnight trading before dropping back on Monday, an unprecedented move that sparked speculation that the central bank may intervene.
The crown traded as high as 23.00 to the euro late European time on Sunday -- a 7.9 percent rise from the close of trading in Prague on Friday.
It then dropped sharply to 24.670 at 1537 GMT on Monday, still 1.2 percent above Friday levels and up from previous all-time high of 24.83 seen on March 4.
Traders said options trading in Asia was behind the move, and some questioned whether there may have been an erroneous trade that set off the rally.
"The move was driven by one-off purchases by foreign players in a little liquid market," said bank CSOB in a report.
"The optimism does not have to wane at the beginning of the week. The sharp drops of the euro/crown pair activated a number of stop-loss selling of euros and dollars, which may resound in the market in the coming days," it said.
It added that if the crown holds on the strong side of 25, it may spark more dovish talk from the central bank. Analysts have been split over the chances of another interest rate hike in the current cycle, following 125 basis point tightening to 3.75 percent since the last spring.
The crown has been rising due to fast economic growth in the central European country, seen as a safe haven with a track record of currency gains.
The Reuters trading system showed one trade worth just 1 million euros at the 23.00 level. There was a trade of at least 10 million at 23.495 and a trade worth 4 million at 23.500.
The central bank (CNB) had no immediate comment on the currency move.
The crown was 11.7 percent higher from a year ago on Monday in local currency terms.
The central bank has seen the crown rise as excessive in the past months. It agreed a deal with the government last week to curb the currency's strength by removing state foreign currency revenues from the market, but has shied from intervention.
"As this morning's move so unquestionably and clearly is unwarranted it creates a test of the CNB's real willingness to prevent a further slide in EUR/CZK," said Commerzbank analyst Ulrich Leuchtmann.
"If it stays inactive or again only is willing to agree on symbolic measures this is an invitation to the market to pull down EUR/CZK as far as it likes. But perhaps this was a wake up call for the CNB."
Analyst Lars Christensen from Danske Bank agreed the chances of intervention have risen, adding the move was a "freak event".
"People were squaring up positions before the IMF (weekend meeting), there was low liquidity. If it had to happen on any day of the year, then this was the day. But it is the black swan that no one expects to go by," he said.
But Citibank analyst Jaromir Sindel said he expected the central bank to stay put for now and see where the crown rate settles in a standard liquid market.
"The central bank will wait until it shows what happens next throughout the week," he said.
"This will influence all the positions closed. It will be interesting how exporters deal with it... there will be many trades that had some stop-losses, they will go into new ones, it will be very interesting."
(Additional reporting by Carolyn Cohn in London) (Reporting by Jan Lopatka, editing by Ian Jones)