U.S. stock index futures fell  as fears about the euro zone's debt crisis overshadowed what appeared to be a buoyant start to the holiday shopping season.

Stocks were facing their worst week in two months and their second consecutive week of losses.

Yields on Italy's debt approached recent highs that sparked a sell-off in world markets. Italy paid a record 6.5 percent to borrow money over six months on Friday, and its longer-term funding costs soared far above levels seen as sustainable for public finances, raising the pressure on Rome's new emergency government.

U.S. stock markets were closed for the Thanksgiving holiday on Thursday and will be open on Friday until 1 p.m. The day after Thanksgiving is typically one of the lightest trading volume days of the year.

World markets:

Nikkei 8,160 -5.17 -0.06%

Hang Seng  17,689 -245.62 -1.37%

Shanghai Composite 2,380 -17.33 -0.72%

FTSE  5,131 +3.50 +0.07%

CAC  2,825 +2.88 +0.10%

DAX  5,448 +19.78 +0.36%

Crude oil: $95.36 (-1,7%).