The selloff in U.S. Treasurys just won't relent, with the yield on the 10-year note hitting a fresh two-decade high in afternoon trading.

The 10-year yield was recently 5.349%, surpassing the last 24-year intraday high of 5.344% set on Thursday, according to Tradeweb.

Yields, which rise when bond prices fall, have climbed steadily throughout the U.S. trading session with no obvious, strong catalyst. That is adding to concerns that the bond selloff might be getting a life of its own, with investors selling Treasurys largely because that's what others are doing.

Analysts said that two factors are likely helping yields rise today:

-- An unexpectedly large increase in the prices paid component of the Institution for Supply Management's service-sector purchasing managers index. Yields didn't immediately respond to the release of the report, but the data nonetheless reinforced concerns about the inflation outlook.

-- Looming bond auctions. The Treasury Department will issue $58 billion of 3-year notes on Tuesday, followed by $39 billion of 10-year notes Wednesday and $22 billion of 30-year bonds on Thursday. Some investors may be nervous about how those auctions will be received, causing them to sell Treasurys ahead of time.