The United States Natural Gas ( UNG) exchanged-traded fund was one of the best performers Friday, thanks to a surge in natural gas prices. Prices were rising on resurfacing concerns over looming storms. Tropical storm Ingrid was the latest to form during the height of hurricane season. Recently, natural gas jumped 27 cents to $6.30 per million British thermal units. The ETF was climbing 98 cents, or 2.6%, to $38.88. ETFs tracking Asian markets were also among the best performers Friday, as Japan's Nikkei 225 Index rose 1.9%, Hong Kong's Hang Seng Index added 1.5% and China's CSI 300 Index gained 0.9%. The SPDR S&P China ( GXC) was adding $1.36, or 1.7%, to $82.36. The iShares FTSE/Xinhua China 25 Index ( FXI) was higher by $2.37, or 1.5%, to $156.05. The PowerShares Golden Dragon Halter USX China ( PGJ) rose 39 cents, or 1.4%, to $28.49. The iShares MSCI Hong Kong Index ( EWH) was up 17 cents, or 0.9%, to $20.10. Homebuilder-related bundled securities were also rising. D.R. Horton ( DHI), Lennar ( LEN), Hovnanian ( HOV) and Toll Brothers ( TOL) all climbed 2.2% or more. The iShares Dow Jones U.S. Home Construction ( ITB) added 29 cents, or 1.4%, to $21.77. The SPDR S&P Homebuilders ( XHB) was up 24 cents, or 1.1%, to $23.15. On the other hand, ETFs tracking European bourses were losing ground after U.K. lender Northern Rock sought emergency funding from the Bank of England, a sign that the subprime mortgage mess was spilling into overseas markets. London's FTSE 100 was down 1.2%, the CAC 40 in Paris was off 0.5% and Germany's Xetra Dax was lower by 0.5%. The iShares MSCI United Kingdom Index ( EWU) was losing 41 cents, or 1.6%, to $24.70. The iShares S&P Europe 350 Index ( IEV) was down $1.39, or 1.2%, to $112.95. The PowerShares Dynamic Europe ( PEH) shed 32 cents, or 1.3%, to $23.78.