The euro reversed earlier losses on Friday after the Swedish central bank said it had increased the euro's share in its foreign exchange reserves to 50 percent.
The move follows dollar-negative comments in recent weeks by Gulf central banks that they are considering increasing the share of the euro in their reserves.
"There's a feeling that central banks hunt in packs so even though Riksbank reserves are relatively small markets will speculate about others doing the same," said Tim Fox, foreign exchange strategist at Dresdner Kleinwort Wasserstein.
The Riksbank said it had reallocated foreign currency reserves over the past four weeks, cutting the dollar's share to 20 percent from 37 percent and raising the euro's share to 50 percent from 37 percent.
It also increased its holding of Norwegian crowns to 10 percent from zero and cut the Japanese yen to zero from eight percent. By 1202 GMT, the euro was flat on the day at $1.2309, having recovered from a session low of $1.2267 hit before Sweden's announcement. The move took it as high as $1.2349 back towards Wednesday's seven-month high of $1.2394.
The dollar was 0.1 percent weaker at 117.12 yen, with traders citing selling by funds and Japanese corporates. The euro was down 0.2 percent at 144.41 yen, despite rising against the currency after Sweden's announcement.
Although Sweden's foreign currency reserves are relatively small, at around $21 billion, the size of the shift was significant, analysts said.
"The move is interesting in the sense that it's come at a time when central bankers have been talking more about global imbalances and about a dollar decline being the only way the US current account deficit could be resolved," said Adarsh Sinha, foreign exchange strategist at Barclays.
"Given these discussions, and if other central bankers think in this manner as well, it could be a big dollar negative."
Earlier in the session the dollar had strengthened as a sell-off in the precious metals market freed up cash to invest in the greenback, helping the US currency to recover from a seven-month low versus the euro hit earlier this week.
Some hedge funds may have to trim their short dollar positions to meet margin calls on long commodity futures positions, particularly gold and silver, a move that could lend support to the dollar.
There is no major US or eurozone data due on Friday, but Group of Seven finance ministers and central bank governors meet in Washington later in the day.