Reuters reports that traders said that China's major state-owned banks were seen buying U.S. dollars at the rate of about 6.52 yuan on Thursday, in a move viewed as an effort to keep the local currency from rising too fast and breaching a key level.

The onshore spot market opened at 6.5204 per dollar and surged to a high of 6.5148 at one point in morning trade, its loftiest since June 22, 2018.

The state bank action quickly dragged the yuan to the weaker side of 6.52 per dollar, four traders told Reuters.

For the year, the yuan has appreciated nearly 7% and is set to book its first annual gain in three.

Another trader said big banks started purchasing the greenback whenever the spot price rose past 6.52, adding the move could be an attempt by authorities to control the pace of yuan appreciation through state banks.

Traders added that 6.52 is widely seen as the ceiling for the yuan for now. A breach of that level could push the yuan over the key rate of 6.5, considered by markets as a new red line for authorities.