The Treasury Department on Wednesday said it will more than double the size of its government debt repurchases, sending yields sharply lower.

With fixed income markets under pressure and yields surging to levels not seen in nearly 20 years, the announcement targets a sensitive part of the Treasury market.

Under the accelerated buyback, Treasury will target the 10- to 20- year and 20- to 30-year portion of the market, which has seen a buyers' strike since late June. The government will "at least double" the maximum size of its buyback operations, from $2 billion to "at least" $4 billion, according to an announcement from the department.

Yields cratered following the announcement.

The benchmark 10-year note fell 6 basis points to 4.647% and the 30-year "long" bond tumbled 9 basis point to 5.196%. A basis point equals 0.01%. Yields and prices move in opposite directions.

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