NEW YORK (AP) _ Bond prices surged in early trading today amid further signs of weak economic growth.

The Treasury's benchmark 30-year bond was up 3/8 point, or $3.75 per $1,000 face amount, around midday. Its yield headed down to 8.50 percent from 8.54 percent late Thursday.

The spurt came after the Commerce Department said the gross national product, the country's total output of goods and services, grew at an annual rate of just 1.2 percent from April through June.

Economists said the report gave further impetus to a belief the economy is sliding into a recession.

Additionally, GNP second-quarter increase followed a revised 1.7 percent increase in the first quarter and a barely discernible 0.3 percent advance in the October-December period last year.

A slowing economy supports the bond market, which attracts buyers to long- term fixed-income securities as a hedge against bad times.

Kevin Flanagan, money market economist for Dean Witter Reynolds Inc., said the rise in bond prices this morning was held back in part by an inflation measure in the GNP report that was higher than expected. Inflation erodes the value of bonds.

Morning trading activity was moderate.

In the secondary market for Treasury bonds, prices of short-term governments were up 3-16 point to 5-16 point, intermediate maturities gained 9-32 point and long-term issues were up as much as 7-16 point, according to Telerate Inc., a financial information service.

The movement of a point is equivalent to a change of $10 in the price of a bond with a $1,000 face value.

The Shearson Lehman Hutton Daily Treasury Bond Index, which measures price movements on all outstanding Treasury issues with maturities of a year or longer, was 3.23 higher at 1,163.25.

Yields on three-month Treasury bills fell to 7.76 percent as the discount was down 5 basis points to 7.52 percent. Yields on six-month bills fell to 7.79 percent as the discount declined 5 basis points to 7.41 percent. Yields on one-year bills fell to 7.77 percent from Thursday's auction as the discount tumbled 11 basis points to 7.25 percent.

A basis point is one-hundredth of a percentage point. The yield is the annualized return on an investment in a Treasury bill. The discount is the percentage that bills are selling below the face value, which is paid at maturity.

The federal funds rate, the interest rate banks charge each other on overnight loans, was quoted at 8 percent, unchanged from late Thursday.