Exchange-traded funds tracking precious metals were among the best performers of Thursday's session, as gold futures topped $700 an ounce for the first time in four months.

Gold prices surged $13.80 to $704.50 an ounce as buyers looked for a safe haven amid news that Syria had fired surface-to-air missiles at Israeli aircraft. Silver was also on the rise, climbing 26 cents to $12.61 an ounce.

The Market Vectors Gold Miners ( GDX) ETF was up $2.22, or 5.8%, to $40.70. The SPDR S&P Metals & Mining ( XME) was adding $1.50, or 2.6%, to $59.38. The PowerShares DB Silver ( DBS) rose 57 cents, or 2.4%, to $24.52. The PowerShares DB Precious Metals ( DBP) was higher by 51 cents, or 2%, to $26.73.

The Biotech HOLDRs ( BBH) was also among winners after holding Biogen Idec ( BIIB) reaffirmed its full-year outlook. The company also said it expects revenue and earnings growth through 2010. Biogen was jumping more than 6%, and the Biotech HOLDRs ETF was up $2.65, or 1.6%, to $171.51.

On the other hand, housing-related ETFs were among the worst decliners of Thursday's session, after the Mortgage Bankers Association released a report that said 5.1% of the loans in its survey were delinquent in the second quarter and that the number of dwellings entering foreclosure hit a record high. Subprime delinquencies rose to 14.8%, the highest since the second quarter of 2002.

Following the release, the Philadelphia Housing Sector Index was off 0.5%. Beazer Homes ( BZH), Hovnanian ( HOV), Centex ( CTX) and Pulte Homes ( PHM) were all trading lower.

The SPDR S&P Homebuilders ( XHB) was down 27 cents, or 1.1%, to $24.09. The iShares Dow Jones U.S. Home Construction ( ITB) was losing 23 cents, or 1%, to $22.79.

The United States Natural Gas ( UNG) was also among the biggest decliners, as natural gas prices slipped 14 cents to $5.67 per million British thermal unit. The ETF was lower by $1.11, or 3.1%, to $35.17.