Stock index futures pointed to a flat open on Thursday after data showed a surprise rise in weekly jobless claims for the second week running, adding to uncertainty over the economic outlook.

The data tempered earlier optimism following a strong rally in Chinese stocks, which helped ease fears that global equity prices have risen too far too fast, following a 20 percent fall in China's equity market over the last two weeks.

Initial claims for state unemployment insurance benefits rose 15,000 to a seasonally adjusted 576,000 last week from 561,000 the prior week, the U.S. Labor Department said.

Analysts polled by Reuters had forecast new claims slipping to 550,000. The news added to concerns that the economic recovery would be slow. Futures prices fell after the report but still pointed to a flat open.

I think it gives more evidence of a U-shaped, versus a V-shaped, recovery, said Steve Goldman, chief market strategist at Weeden & Co in Greenwich, Connecticut. For stocks, we've got a little bit of a disappointment as we are getting closer to new recovery highs once again.

S&P 500 futures fell 2.4 points, about even with fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 16 points, and Nasdaq 100 futures fell 5.0 points.